When the RowMatchType is set to With Parameter, this property is visible: enter a valid name for a .NET parameter.

 

The value entered in this property will be surfaced to the caller of the containing Web service method in order to provide a runtime value for auto-selection.

 

At runtime, the value of the parameter named based on this property will be used to match with the RowMatchField: when the two values are equal, the active row will be selected.