OleDbCommand.Prepare Method

Definition

Namespace:

System.Data.OleDb

Assembly:

System.Data.OleDb.dll

Package:

System.Data.OleDb v9.0.0-rc.2.24473.5

Source:

OleDbCommand.cs

Creates a prepared (or compiled) version of the command on the data source.

public:
 override void Prepare();

public override void Prepare ();

override this.Prepare : unit -> unit

Public Overrides Sub Prepare ()

Implements

Prepare()

Exceptions

InvalidOperationException

The Connection is not set.

-or-

The Connection is not open.

Examples

The following example creates an OleDbCommand and opens the connection. The example then prepares a stored procedure on the data source by passing a string that is an SQL SELECT statement and a string to use to connect to the data source.

private static void OleDbCommandPrepare(string connectionString)
{
    using (OleDbConnection connection = new
               OleDbConnection(connectionString))
    {
        connection.Open();

        // Create the Command.
        OleDbCommand command = new OleDbCommand();

        // Set the Connection, CommandText and Parameters.
        command.Connection = connection;
        command.CommandText =
            "INSERT INTO dbo.Region (RegionID, RegionDescription) VALUES (?, ?)";
        command.Parameters.Add("RegionID", OleDbType.Integer, 4);
        command.Parameters.Add("RegionDescription", OleDbType.VarWChar, 50);
        command.Parameters[0].Value = 20;
        command.Parameters[1].Value = "First Region";

        // Call  Prepare and ExecuteNonQuery.
        command.Prepare();
        command.ExecuteNonQuery();

        // Change parameter values and call ExecuteNonQuery.
        command.Parameters[0].Value = 21;
        command.Parameters[1].Value = "SecondRegion";
        command.ExecuteNonQuery();
    }
}

Public Sub OleDbCommandPrepare(ByVal connectionString As String)

    Using connection As OleDbConnection = New _
        OleDbConnection(connectionString)
        connection.Open()

        ' Create the Command.
        Dim command As New OleDbCommand()

        ' Set the Connection, CommandText and Parameters.
        command.Connection = connection
        command.CommandText = _
          "INSERT INTO dbo.Region (RegionID, RegionDescription) VALUES (?, ?);"
        command.Parameters.Add("RegionID", OleDbType.Integer, 4)
        command.Parameters.Add("RegionDescription", OleDbType.VarWChar, 50)
        command.Parameters(0).Value = 20
        command.Parameters(1).Value = "First Region"

        ' Call  Prepare and ExecuteNonQuery.
        command.Prepare()
        command.ExecuteNonQuery()

        ' Change parameter values and call ExecuteNonQuery.
        command.Parameters(0).Value = 21
        command.Parameters(1).Value = "Second Region"
        command.ExecuteNonQuery()
    End Using
End Sub

Remarks

If the CommandType property is set to TableDirect, Prepare does nothing. If CommandType is set to StoredProcedure, the call to Prepare should succeed, although it may cause a no-op.

Before you call Prepare, specify the data type of each parameter in the statement to be prepared. For each parameter that has a variable length data type, you must set the Size property to the maximum size needed. Prepare returns an error if these conditions are not met.

If you call an Execute method after you call Prepare, any parameter value that is larger than the value specified by the Size property is automatically truncated to the original specified size of the parameter, and no truncation errors are returned.

Output parameters (whether prepared or not) must have a user-specified data type. If you specify a variable length data type, you must also specify the maximum Size.

See also

• Working with Commands