The value of the ObjectDataSourceView.OldValuesParameterFormatString property is applied to primary keys only, such as those that are identified with the DataKeyNames property of a data-bound control, or in delete and update scenarios where the ObjectDataSourceView.ConflictDetection property is set to the System.Web.UI.ConflictOptions.CompareAllValues value, and the set of original values are passed to the corresponding data method.

The following are two common scenarios where you might change the ObjectDataSourceView.OldValuesParameterFormatString property:

• You might want to change the property to differentiate between old and new values in updates. When the ObjectDataSourceView.ConflictDetection property is set to the System.Web.UI.ConflictOptions.CompareAllValues value, parameters for both the original and new values are added to the ObjectDataSource.UpdateParameters collection. Without the formatting string, two parameters with the same name would be created for each data field. By changing the name of the original value parameter, you can compare the data to the original data source to detect conflicts and compare key values.

• Some visual designers implement a particular naming scheme for original values and keys.

The ObjectDataSource.OldValuesParameterFormatString property delegates to the ObjectDataSourceView.OldValuesParameterFormatString property of the System.Web.UI.WebControls.ObjectDataSourceView object that is associated with the System.Web.UI.WebControls.ObjectDataSource control.