Handling DataAdapter Events

Handling DataAdapter Events

DataAdapter supports only two events:

OnRowUpdating and OnRowUpdated. T

hese two events occur on either side of the actual dataset update, providing fine control of the process.

1)OnRowUpdating Event

The OnRowUpdating event is raised after the Update method has set the parameter values of the command to be executed but before the command is executed.

 The event handler for this event receives an argument whose properties provide essential information about the command that is about to be executed.

The class of the event arguments is defined by the Data Provider, so it will be either OleDbRowUpdatingEventArgs or SqlRowUpdatingEventArgs if one of the .NET

Framework Data Providers is used.

RowUpdatingEventArgs Properties

Command:-The Data Command to be executed.

Errors:-The errors generated by the .NET Data Provider

Row:-The DataReader to be updated

StatementType:-The type of Command tobe executed.The possiblevalues are Select, Insert Delete, and Update

Status:-The UpdateStatus of the Command

TableMapping:-The DataTableMap ping used by the update

2)OnRowUpdated Event

The OnRowUpdated event is raised after the Update method executes the appropriate

command against the data source. The event handler for this event is either passed an

SqlRowUpdatedEventArgs or an OleDbRowUpdatedEventArgs argument, depending on

the Data Provider.

Example:-

// Assumes that connection is a valid SqlConnection object. SqlDataAdapter sda = new SqlDataAdapter( "SELECT EmpID, EmpName FROM Emp", connection); // Add handlers. sda.RowUpdating += new SqlRowUpdatingEventHandler(OnRowUpdating); sda.RowUpdated += new SqlRowUpdatedEventHandler(OnRowUpdated); // Set DataAdapter command properties, fill DataSet, modify DataSet. sda.Update(ds, "Emp"); // Remove handlers. sda.RowUpdating -= new SqlRowUpdatingEventHandler(OnRowUpdating); sda.RowUpdated -= new SqlRowUpdatedEventHandler(OnRowUpdated); protected static void OnRowUpdating( object sender, SqlRowUpdatingEventArgs args) { if (args.StatementType == StatementType.Delete) { System.IO.TextWriter tw = System.IO.File.AppendText("Deletes.log"); tw.WriteLine( "{0}: Customer {1} Deleted.", DateTime.Now, args.Row["EmpID", DataRowVersion.Original]); tw.Close(); } } protected static void OnRowUpdated( object sender, SqlRowUpdatedEventArgs args) { if (args.Status == UpdateStatus.ErrorsOccurred) { args.Row.RowError = args.Errors.Message; args.Status = UpdateStatus.SkipCurrentRow; } }