# Class NpgsqlConnection

Namespace
  Npgsql

Assembly
  Npgsql.dll

This class represents a connection to a PostgreSQL server.

    public sealed class NpgsqlConnection : DbConnection, IDbConnection, IAsyncDisposable, ICloneable, IComponent, IDisposable

Inheritance
  object
  MarshalByRefObject
  Component
  DbConnection
  NpgsqlConnection

Implements
  IDbConnection
  IAsyncDisposable
  ICloneable
  IComponent
  IDisposable

Inherited Members
  DbConnection.ChangeDatabaseAsync(string, CancellationToken)
  DbConnection.OpenAsync()
  DbConnection.StateChange
  Component.Dispose()
  Component.ToString()
  Component.Container
  Component.Site
  Component.Disposed
  MarshalByRefObject.GetLifetimeService()
  MarshalByRefObject.InitializeLifetimeService()
  object.Equals(object)
  object.Equals(object, object)
  object.GetHashCode()
  object.GetType()
  object.ReferenceEquals(object, object)

## Constructors

### NpgsqlConnection()

Initializes a new instance of the NpgsqlConnection class.

    public NpgsqlConnection()

### NpgsqlConnection(string?)

Initializes a new instance of NpgsqlConnection with the given connection string.

    public NpgsqlConnection(string? connectionString)

#### Parameters

`connectionString` string

  The connection used to open the PostgreSQL database.

## Fields

### DefaultPort

The default TCP/IP port for PostgreSQL.

    public const int DefaultPort = 27500

#### Field Value

int

## Properties

### CanCreateBatch

Gets a value that indicates whether this DbConnection instance supports the DbBatch class.

    public override bool CanCreateBatch { get; }

#### Property Value

bool

  true if this instance supports the DbBatch class; otherwise, false. The default is false.

### CommandTimeout

Gets the time (in seconds) to wait while trying to execute a command before terminating the attempt and generating an error.

    public int CommandTimeout { get; }

#### Property Value

int

  The time (in seconds) to wait for a command to complete. The default value is 30 seconds.

### ConnectionString

Gets or sets the string used to connect to a PostgreSQL database. See the manual for details.

    [AllowNull]
    public override string ConnectionString { get; set; }

#### Property Value

string

  The connection string that includes the server name, the database name, and other parameters needed to establish the initial connection. The default value is an empty string.

### ConnectionTimeout

Gets the time (in seconds) to wait while trying to establish a connection before terminating the attempt and generating an error.

    public override int ConnectionTimeout { get; }

#### Property Value

int

  The time (in seconds) to wait for a connection to open. The default value is 15 seconds.

### DataSource

Gets the string identifying the database server (host and port)

    public override string DataSource { get; }

#### Property Value

string

  The name of the database server (host and port). If the connection uses a Unix-domain socket, the path to that socket is returned. The default value is the empty string.

### Database

Gets the name of the current database or the database to be used after a connection is opened.

    public override string Database { get; }

#### Property Value

string

  The name of the current database or the name of the database to be used after a connection is opened. The default value is the empty string.

### DbProviderFactory

DB provider factory.

    protected override DbProviderFactory DbProviderFactory { get; }

#### Property Value

DbProviderFactory

### FullState

Gets the current state of the connection.

    [Browsable(false)]
    public ConnectionState FullState { get; }

#### Property Value

ConnectionState

  A bitwise combination of the ConnectionState values. The default is Closed.

### GlobalTypeMapper

The global type mapper, which contains defaults used by all new connections. Modify mappings on this mapper to affect your entire application.

    [Obsolete("Global-level type mapping has been replaced with data source mapping, see the 7.0 release notes.")]
    public static INpgsqlTypeMapper GlobalTypeMapper { get; }

#### Property Value

INpgsqlTypeMapper

### HasIntegerDateTimes

Reports whether the backend uses the newer integer timestamp representation. Note that the old floating point representation is not supported. Meant for use by type plugins (e.g. NodaTime)

    [Browsable(false)]
    public bool HasIntegerDateTimes { get; }

#### Property Value

bool

### Host

Backend server host name.

    [Browsable(true)]
    public string? Host { get; }

#### Property Value

string

### Port

Backend server port.

    [Browsable(true)]
    public int Port { get; }

#### Property Value

int

### PostgreSqlVersion

The version of the PostgreSQL server we're connected to.

This can only be called when the connection is open.

In case of a development or pre-release version this field will contain the version of the next version to be released from this branch.

    [Browsable(false)]
    public Version PostgreSqlVersion { get; }

#### Property Value

Version

### PostgresParameters

Holds all PostgreSQL parameters received for this connection. Is updated if the values change (e.g. as a result of a SET command).

    [Browsable(false)]
    public IReadOnlyDictionary<string, string> PostgresParameters { get; }

#### Property Value

IReadOnlyDictionary<string, string>

### ProcessID

Process id of backend server. This can only be called when there is an active connection.

    [Browsable(false)]
    public int ProcessID { get; }

#### Property Value

int

### ProvideClientCertificatesCallback

Selects the local Secure Sockets Layer (SSL) certificate used for authentication.

    public ProvideClientCertificatesCallback? ProvideClientCertificatesCallback { get; set; }

#### Property Value

ProvideClientCertificatesCallback

#### Remarks

See https://msdn.microsoft.com/en-us/library/system.net.security.localcertificateselectioncallback(v=vs.110).aspx

### ProvidePasswordCallback

Gets or sets the delegate used to generate a password for new database connections.

    [Obsolete("Use NpgsqlDataSourceBuilder.UsePeriodicPasswordProvider or inject passwords directly into NpgsqlDataSource.Password")]
    public ProvidePasswordCallback? ProvidePasswordCallback { get; set; }

#### Property Value

ProvidePasswordCallback

#### Remarks

This delegate is executed when a new database connection is opened that requires a password.

The Password and Passfile connection string properties have precedence over this delegate: it will not be executed if a password is specified, or if the specified or default Passfile contains a valid entry.

Due to connection pooling this delegate is only executed when a new physical connection is opened, not when reusing a connection that was previously opened from the pool.

### ServerVersion

The PostgreSQL server version as returned by the server_version option. This can only be called when the connection is open.

    public override string ServerVersion { get; }

#### Property Value

string

### State

Gets whether the current state of the connection is Open or Closed

    [Browsable(false)]
    public override ConnectionState State { get; }

#### Property Value

ConnectionState

  ConnectionState.Open, ConnectionState.Closed or ConnectionState.Connecting

### Timezone

The connection's timezone as reported by PostgreSQL, in the IANA/Olson database format.

    [Browsable(false)]
    public string Timezone { get; }

#### Property Value

string

### TypeMapper

Connection-level type mapping is no longer supported. See the 7.0 release notes for configuring type mapping on NpgsqlDataSource.

    [Obsolete("Connection-level type mapping is no longer supported. See the 7.0 release notes for configuring type mapping on NpgsqlDataSource.", true)]
    public INpgsqlTypeMapper TypeMapper { get; }

#### Property Value

INpgsqlTypeMapper

### UserCertificateValidationCallback

When using SSL/TLS, this is a callback that allows customizing how the PostgreSQL-provided certificate is verified. This is an advanced API, consider using VerifyFull or VerifyCA instead.

    public RemoteCertificateValidationCallback? UserCertificateValidationCallback { get; set; }

#### Property Value

RemoteCertificateValidationCallback

#### Remarks

Cannot be used in conjunction with Disable, VerifyCA and VerifyFull.

See https://msdn.microsoft.com/en-us/library/system.net.security.remotecertificatevalidationcallback(v=vs.110).aspx.

### UserName

User name.

    public string? UserName { get; }

#### Property Value

string

## Methods

### BeginBinaryExport(string)

Begins a binary COPY TO STDOUT operation, a high-performance data export mechanism from a PostgreSQL table.

    public NpgsqlBinaryExporter BeginBinaryExport(string copyToCommand)

#### Parameters

`copyToCommand` string

  A COPY TO STDOUT SQL command

#### Returns

NpgsqlBinaryExporter

  A NpgsqlBinaryExporter which can be used to read rows and columns

#### Remarks

See https://www.postgresql.org/docs/current/static/sql-copy.html.

### BeginBinaryExportAsync(string, CancellationToken)

Begins a binary COPY TO STDOUT operation, a high-performance data export mechanism from a PostgreSQL table.

    public Task<NpgsqlBinaryExporter> BeginBinaryExportAsync(string copyToCommand, CancellationToken cancellationToken = default)

#### Parameters

`copyToCommand` string

  A COPY TO STDOUT SQL command

`cancellationToken` CancellationToken

  An optional token to cancel the asynchronous operation. The default value is None.

#### Returns

Task<NpgsqlBinaryExporter>

  A NpgsqlBinaryExporter which can be used to read rows and columns

#### Remarks

See https://www.postgresql.org/docs/current/static/sql-copy.html.

### BeginBinaryImport(string)

Begins a binary COPY FROM STDIN operation, a high-performance data import mechanism to a PostgreSQL table.

    public NpgsqlBinaryImporter BeginBinaryImport(string copyFromCommand)

#### Parameters

`copyFromCommand` string

  A COPY FROM STDIN SQL command

#### Returns

NpgsqlBinaryImporter

  A NpgsqlBinaryImporter which can be used to write rows and columns

#### Remarks

See https://www.postgresql.org/docs/current/static/sql-copy.html.

### BeginBinaryImportAsync(string, CancellationToken)

Begins a binary COPY FROM STDIN operation, a high-performance data import mechanism to a PostgreSQL table.

    public Task<NpgsqlBinaryImporter> BeginBinaryImportAsync(string copyFromCommand, CancellationToken cancellationToken = default)

#### Parameters

`copyFromCommand` string

  A COPY FROM STDIN SQL command

`cancellationToken` CancellationToken

  An optional token to cancel the asynchronous operation. The default value is None.

#### Returns

Task<NpgsqlBinaryImporter>

  A NpgsqlBinaryImporter which can be used to write rows and columns

#### Remarks

See https://www.postgresql.org/docs/current/static/sql-copy.html.

### BeginDbTransaction(IsolationLevel)

Begins a database transaction with the specified isolation level.

    protected override DbTransaction BeginDbTransaction(IsolationLevel isolationLevel)

#### Parameters

`isolationLevel` IsolationLevel

  The isolation level under which the transaction should run.

#### Returns

DbTransaction

  A DbTransaction object representing the new transaction.

#### Remarks

Nested transactions are not supported.

### BeginDbTransactionAsync(IsolationLevel, CancellationToken)

Asynchronously begins a database transaction.

    protected override ValueTask<DbTransaction> BeginDbTransactionAsync(IsolationLevel isolationLevel, CancellationToken cancellationToken)

#### Parameters

`isolationLevel` IsolationLevel

  The isolation level under which the transaction should run.

`cancellationToken` CancellationToken

  An optional token to cancel the asynchronous operation. The default value is None.

#### Returns

ValueTask<DbTransaction>

  A task whose Result property is an object representing the new transaction.

#### Remarks

Nested transactions are not supported.

### BeginRawBinaryCopy(string)

Begins a raw binary COPY operation (TO STDOUT or FROM STDIN), a high-performance data export/import mechanism to a PostgreSQL table. Note that unlike the other COPY API methods, BeginRawBinaryCopy(string) doesn't implement any encoding/decoding and is unsuitable for structured import/export operation. It is useful mainly for exporting a table as an opaque blob, for the purpose of importing it back later.

    public NpgsqlRawCopyStream BeginRawBinaryCopy(string copyCommand)

#### Parameters

`copyCommand` string

  A COPY TO STDOUT or COPY FROM STDIN SQL command

#### Returns

NpgsqlRawCopyStream

  A NpgsqlRawCopyStream that can be used to read or write raw binary data.

#### Remarks

See https://www.postgresql.org/docs/current/static/sql-copy.html.

### BeginRawBinaryCopyAsync(string, CancellationToken)

Begins a raw binary COPY operation (TO STDOUT or FROM STDIN), a high-performance data export/import mechanism to a PostgreSQL table. Note that unlike the other COPY API methods, BeginRawBinaryCopyAsync(string, CancellationToken) doesn't implement any encoding/decoding and is unsuitable for structured import/export operation. It is useful mainly for exporting a table as an opaque blob, for the purpose of importing it back later.

    public Task<NpgsqlRawCopyStream> BeginRawBinaryCopyAsync(string copyCommand, CancellationToken cancellationToken = default)

#### Parameters

`copyCommand` string

  A COPY TO STDOUT or COPY FROM STDIN SQL command

`cancellationToken` CancellationToken

  An optional token to cancel the asynchronous operation. The default value is None.

#### Returns

Task<NpgsqlRawCopyStream>

  A NpgsqlRawCopyStream that can be used to read or write raw binary data.

#### Remarks

See https://www.postgresql.org/docs/current/static/sql-copy.html.

### BeginTextExport(string)

Begins a textual COPY TO STDOUT operation, a data export mechanism from a PostgreSQL table. It is the user's responsibility to parse the textual input according to the format specified in `copyToCommand`.

    public TextReader BeginTextExport(string copyToCommand)

#### Parameters

`copyToCommand` string

  A COPY TO STDOUT SQL command

#### Returns

TextReader

  A TextReader that can be used to read textual data.

#### Remarks

See https://www.postgresql.org/docs/current/static/sql-copy.html.

### BeginTextExportAsync(string, CancellationToken)

Begins a textual COPY TO STDOUT operation, a data export mechanism from a PostgreSQL table. It is the user's responsibility to parse the textual input according to the format specified in `copyToCommand`.

    public Task<TextReader> BeginTextExportAsync(string copyToCommand, CancellationToken cancellationToken = default)

#### Parameters

`copyToCommand` string

  A COPY TO STDOUT SQL command

`cancellationToken` CancellationToken

  An optional token to cancel the asynchronous operation. The default value is None.

#### Returns

Task<TextReader>

  A TextReader that can be used to read textual data.

#### Remarks

See https://www.postgresql.org/docs/current/static/sql-copy.html.

### BeginTextImport(string)

Begins a textual COPY FROM STDIN operation, a data import mechanism to a PostgreSQL table. It is the user's responsibility to send the textual input according to the format specified in `copyFromCommand`.

    public TextWriter BeginTextImport(string copyFromCommand)

#### Parameters

`copyFromCommand` string

  A COPY FROM STDIN SQL command

#### Returns

TextWriter

  A TextWriter that can be used to send textual data.

#### Remarks

See https://www.postgresql.org/docs/current/static/sql-copy.html.

### BeginTextImportAsync(string, CancellationToken)

Begins a textual COPY FROM STDIN operation, a data import mechanism to a PostgreSQL table. It is the user's responsibility to send the textual input according to the format specified in `copyFromCommand`.

    public Task<TextWriter> BeginTextImportAsync(string copyFromCommand, CancellationToken cancellationToken = default)

#### Parameters

`copyFromCommand` string

  A COPY FROM STDIN SQL command

`cancellationToken` CancellationToken

  An optional token to cancel the asynchronous operation. The default value is None.

#### Returns

Task<TextWriter>

  A TextWriter that can be used to send textual data.

#### Remarks

See https://www.postgresql.org/docs/current/static/sql-copy.html.

### BeginTransaction()

Begins a database transaction.

    public NpgsqlTransaction BeginTransaction()

#### Returns

NpgsqlTransaction

  A NpgsqlTransaction object representing the new transaction.

#### Remarks

Nested transactions are not supported. Transactions created by this method will have the ReadCommitted isolation level.

### BeginTransaction(IsolationLevel)

Begins a database transaction with the specified isolation level.

    public NpgsqlTransaction BeginTransaction(IsolationLevel level)

#### Parameters

`level` IsolationLevel

  The isolation level under which the transaction should run.

#### Returns

NpgsqlTransaction

  A NpgsqlTransaction object representing the new transaction.

#### Remarks

Nested transactions are not supported.

### BeginTransactionAsync(IsolationLevel, CancellationToken)

Asynchronously begins a database transaction.

    public ValueTask<NpgsqlTransaction> BeginTransactionAsync(IsolationLevel level, CancellationToken cancellationToken = default)

#### Parameters

`level` IsolationLevel

  The isolation level under which the transaction should run.

`cancellationToken` CancellationToken

  An optional token to cancel the asynchronous operation. The default value is None.

#### Returns

ValueTask<NpgsqlTransaction>

  A task whose Result property is an object representing the new transaction.

#### Remarks

Nested transactions are not supported.

### BeginTransactionAsync(CancellationToken)

Asynchronously begins a database transaction.

    public ValueTask<NpgsqlTransaction> BeginTransactionAsync(CancellationToken cancellationToken = default)

#### Parameters

`cancellationToken` CancellationToken

  An optional token to cancel the asynchronous operation. The default value is None.

#### Returns

ValueTask<NpgsqlTransaction>

  A task whose Result property is an object representing the new transaction.

#### Remarks

Nested transactions are not supported. Transactions created by this method will have the ReadCommitted isolation level.

### ChangeDatabase(string)

This method changes the current database by disconnecting from the actual database and connecting to the specified.

    public override void ChangeDatabase(string dbName)

#### Parameters

`dbName` string

  The name of the database to use in place of the current database.

### ClearAllPools()

Clear all connection pools. All idle physical connections in all pools are immediately closed, and any busy connections which were opened before ClearAllPools() was called will be closed when returned to their pool.

    public static void ClearAllPools()

### ClearPool(NpgsqlConnection)

Clears the connection pool. All idle physical connections in the pool of the given connection are immediately closed, and any busy connections which were opened before ClearPool(NpgsqlConnection) was called will be closed when returned to the pool.

    public static void ClearPool(NpgsqlConnection connection)

#### Parameters

`connection` NpgsqlConnection

### CloneWith(string)

Clones this connection, replacing its connection string with the given one. This allows creating a new connection with the same security information (password, SSL callbacks) while changing other connection parameters (e.g. database or pooling)

    public NpgsqlConnection CloneWith(string connectionString)

#### Parameters

`connectionString` string

#### Returns

NpgsqlConnection

### Close()

Releases the connection. If the connection is pooled, it will be returned to the pool and made available for re-use. If it is non-pooled, the physical connection will be closed.

    public override void Close()

### CloseAsync()

Releases the connection. If the connection is pooled, it will be returned to the pool and made available for re-use. If it is non-pooled, the physical connection will be closed.

    public override Task CloseAsync()

#### Returns

Task

### CreateBatch()

Returns a new instance of the provider's class that implements the DbBatch class.

    public NpgsqlBatch CreateBatch()

#### Returns

NpgsqlBatch

  A new instance of DbBatch.

### CreateCommand()

Creates and returns a NpgsqlCommand object associated with the NpgsqlConnection.

    public NpgsqlCommand CreateCommand()

#### Returns

NpgsqlCommand

  A NpgsqlCommand object.

### CreateDbBatch()

When overridden in a derived class, returns a new instance of the provider's class that implements the DbBatch class.

    protected override DbBatch CreateDbBatch()

#### Returns

DbBatch

  A new instance of DbBatch.

### CreateDbCommand()

Creates and returns a DbCommand object associated with the DbConnection.

    protected override DbCommand CreateDbCommand()

#### Returns

DbCommand

  A DbCommand object.

### Dispose(bool)

Releases all resources used by the NpgsqlConnection.

    protected override void Dispose(bool disposing)

#### Parameters

`disposing` bool

  true when called from Dispose(bool); false when being called from the finalizer.

### DisposeAsync()

Releases all resources used by the NpgsqlConnection.

    public override ValueTask DisposeAsync()

#### Returns

ValueTask

### EnlistTransaction(Transaction?)

Enlist transaction.

    public override void EnlistTransaction(Transaction? transaction)

#### Parameters

`transaction` Transaction

### GetSchema()

Returns the supported collections

    public override DataTable GetSchema()

#### Returns

DataTable

### GetSchema(string?)

Returns the schema collection specified by the collection name.

    public override DataTable GetSchema(string? collectionName)

#### Parameters

`collectionName` string

  The collection name.

#### Returns

DataTable

  The collection specified.

### GetSchema(string?, string?[]?)

Returns the schema collection specified by the collection name filtered by the restrictions.

    public override DataTable GetSchema(string? collectionName, string?[]? restrictions)

#### Parameters

`collectionName` string

  The collection name.

`restrictions` string[]

  The restriction values to filter the results. A description of the restrictions is contained in the Restrictions collection.

#### Returns

DataTable

  The collection specified.

### GetSchemaAsync(string, string?[]?, CancellationToken)

Asynchronously returns the schema collection specified by the collection name filtered by the restrictions.

    public override Task<DataTable> GetSchemaAsync(string collectionName, string?[]? restrictions, CancellationToken cancellationToken = default)

#### Parameters

`collectionName` string

  The collection name.

`restrictions` string[]

  The restriction values to filter the results. A description of the restrictions is contained in the Restrictions collection.

`cancellationToken` CancellationToken

  An optional token to cancel the asynchronous operation. The default value is None.

#### Returns

Task<DataTable>

  The collection specified.

### GetSchemaAsync(string, CancellationToken)

Asynchronously returns the schema collection specified by the collection name.

    public override Task<DataTable> GetSchemaAsync(string collectionName, CancellationToken cancellationToken = default)

#### Parameters

`collectionName` string

  The collection name.

`cancellationToken` CancellationToken

  An optional token to cancel the asynchronous operation. The default value is None.

#### Returns

Task<DataTable>

  The collection specified.

### GetSchemaAsync(CancellationToken)

Asynchronously returns the supported collections.

    public override Task<DataTable> GetSchemaAsync(CancellationToken cancellationToken = default)

#### Parameters

`cancellationToken` CancellationToken

  An optional token to cancel the asynchronous operation. The default value is None.

#### Returns

Task<DataTable>

  The collection specified.

### Open()

Opens a database connection with the property settings specified by the ConnectionString.

    public override void Open()

### OpenAsync(CancellationToken)

This is the asynchronous version of Open().

    public override Task OpenAsync(CancellationToken cancellationToken)

#### Parameters

`cancellationToken` CancellationToken

  An optional token to cancel the asynchronous operation. The default value is None.

#### Returns

Task

  A task representing the asynchronous operation.

#### Remarks

Do not invoke other methods and properties of the NpgsqlConnection object until the returned Task is complete.

### ReloadTypes()

Flushes the type cache for this connection's connection string and reloads the types for this connection only. Type changes will appear for other connections only after they are re-opened from the pool.

    public void ReloadTypes()

### ReloadTypesAsync()

Flushes the type cache for this connection's connection string and reloads the types for this connection only. Type changes will appear for other connections only after they are re-opened from the pool.

    public Task ReloadTypesAsync()

#### Returns

Task

### UnprepareAll()

Unprepares all prepared statements on this connection.

    public void UnprepareAll()

### Wait()

Waits until an asynchronous PostgreSQL messages (e.g. a notification) arrives, and exits immediately. The asynchronous message is delivered via the normal events (Notification, Notice).

    public void Wait()

### Wait(int)

Waits until an asynchronous PostgreSQL messages (e.g. a notification) arrives, and exits immediately. The asynchronous message is delivered via the normal events (Notification, Notice).

    public bool Wait(int timeout)

#### Parameters

`timeout` int

  The time-out value, in milliseconds, passed to ReceiveTimeout. The default value is 0, which indicates an infinite time-out period. Specifying -1 also indicates an infinite time-out period.

#### Returns

bool

  true if an asynchronous message was received, false if timed out.

### Wait(TimeSpan)

Waits until an asynchronous PostgreSQL messages (e.g. a notification) arrives, and exits immediately. The asynchronous message is delivered via the normal events (Notification, Notice).

    public bool Wait(TimeSpan timeout)

#### Parameters

`timeout` TimeSpan

  The time-out value is passed to ReceiveTimeout.

#### Returns

bool

  true if an asynchronous message was received, false if timed out.

### WaitAsync(int, CancellationToken)

Waits asynchronously until an asynchronous PostgreSQL messages (e.g. a notification) arrives, and exits immediately. The asynchronous message is delivered via the normal events (Notification, Notice).

    public Task<bool> WaitAsync(int timeout, CancellationToken cancellationToken = default)

#### Parameters

`timeout` int

  The time-out value, in milliseconds. The default value is 0, which indicates an infinite time-out period. Specifying -1 also indicates an infinite time-out period.

`cancellationToken` CancellationToken

  An optional token to cancel the asynchronous operation. The default value is None.

#### Returns

Task<bool>

  true if an asynchronous message was received, false if timed out.

### WaitAsync(CancellationToken)

Waits asynchronously until an asynchronous PostgreSQL messages (e.g. a notification) arrives, and exits immediately. The asynchronous message is delivered via the normal events (Notification, Notice).

    public Task WaitAsync(CancellationToken cancellationToken = default)

#### Parameters

`cancellationToken` CancellationToken

  An optional token to cancel the asynchronous operation. The default value is None.

#### Returns

Task

### WaitAsync(TimeSpan, CancellationToken)

Waits asynchronously until an asynchronous PostgreSQL messages (e.g. a notification) arrives, and exits immediately. The asynchronous message is delivered via the normal events (Notification, Notice).

    public Task<bool> WaitAsync(TimeSpan timeout, CancellationToken cancellationToken = default)

#### Parameters

`timeout` TimeSpan

  The time-out value as TimeSpan

`cancellationToken` CancellationToken

  An optional token to cancel the asynchronous operation. The default value is None.

#### Returns

Task<bool>

  true if an asynchronous message was received, false if timed out.

## Events

### Notice

Fires when PostgreSQL notices are received from PostgreSQL.

    public event NoticeEventHandler? Notice

#### Event Type

NoticeEventHandler

#### Remarks

PostgreSQL notices are non-critical messages generated by PostgreSQL, either as a result of a user query (e.g. as a warning or informational notice), or due to outside activity (e.g. if the database administrator initiates a "fast" database shutdown).

Note that notices are very different from notifications (see the Notification event).

### Notification

Fires when PostgreSQL notifications are received from PostgreSQL.

    public event NotificationEventHandler? Notification

#### Event Type

NotificationEventHandler

#### Remarks

PostgreSQL notifications are sent when your connection has registered for notifications on a specific channel via the LISTEN command. NOTIFY can be used to generate such notifications, allowing for an inter-connection communication channel.

Note that notifications are very different from notices (see the Notice event).