'Declaration Public Overloads Function BeginExecuteXmlReader() As IAsyncResult
public IAsyncResult BeginExecuteXmlReader()
'Declaration Public Overloads Function BeginExecuteXmlReader() As IAsyncResult
public IAsyncResult BeginExecuteXmlReader()
BeginExecuteXmlReader method enables you to execute a Transact-SQL statement, that has a valid FOR XML clause or returns NTEXT or NVARCHAR data that contains valid XML, or the contents of a column defined with the XML data type, without having current thread blocked. In other words, your program can continue execution while the query runs on a database so you do not have to wait for it.
Refer to "Asynchronous Query Execution" article for detailed information.
To start running a query, you have to call BeginExecuteXmlReader method, which in turn invokes appropriate actions in another thread. Return value of this method must be assigned to an System.IAsyncResult object. After executing this method, the program flow continues.
When you are ready to accept query results, call EndExecuteXmlReader. If at the moment you call this function the query execution has not yet been finished, application stops and waits till the function returns. Then you can treat a System.Xml.XmlReader in a common way.
public void Async_Exec(DbConnectionBase myConnection) { DbCommandBase myCommand = (DbCommandBase)myConnection.CreateCommand(); myCommand.CommandText = "SELECT * FROM Test.Dept"; Console.WriteLine("Starting asynchronous retrieval of data..."); myConnection.Open(); IAsyncResult cres = myCommand.BeginExecuteReader(); if (cres.IsCompleted) Console.WriteLine("Completed."); else Console.WriteLine("Have to wait for operation to complete..."); DbDataReader myReader = myCommand.EndExecuteReader(cres); try { while (myReader.Read()) { Console.WriteLine(myReader.GetInt32(0) + " " + myReader.GetString(1) + " " + myReader.GetString(2)); } } finally { myReader.Close(); myConnection.Close(); } }
Public Sub Async_Exec(ByVal myConnection As DbConnectionBase) Dim myCommand As DbCommandBase = myConnection.CreateCommand() myCommand.CommandText = "SELECT * FROM Test.Dept" Console.WriteLine("Starting asynchronous retrieval of data...") myConnection.Open() Dim cres As IAsyncResult = myCommand.BeginExecuteReader() If cres.IsCompleted Then Console.WriteLine("Completed.") Else Console.WriteLine("Have to wait for operation to complete...") End If Dim myReader As DbDataReader = myCommand.EndExecuteReader(cres) Try While myReader.Read() Console.WriteLine(String.Concat(myReader.GetInt32(0).ToString(), " ", myReader.GetString(1), " ", myReader.GetString(2))) End While Finally myReader.Close() myConnection.Close() End Try End Sub
Target Platforms: Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2