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Thursday, September 14, 2006

Programmatically Setting the ObjectDataSource's Parameter Values in .NET

Programmatically Setting the ObjectDataSource's Parameter Values in .NET

As we saw in the previous tutorial, a number of options are available for declaratively passing parameter values to the ObjectDataSource's methods. If the parameter value is hard-coded, comes from a Web control on the page, or is in any other source that is readable by a data source Parameter object, for example, that value can be bound to the input parameter without writing a line of code.

There may be times, however, when the parameter value comes from some source not already accounted for by one of the built-in data source Parameter objects. If our site supported user accounts we might want to set the parameter based on the currently logged in visitor's User ID. Or we may need to customize the parameter value before sending it along to the ObjectDataSource's underlying object's method.

Whenever the ObjectDataSource's Select method is invoked the ObjectDataSource first raises its Selecting event. The ObjectDataSource's underlying object's method is then invoked. Once that completes the ObjectDataSource's Selected event fires (Figure 1 illustrates this sequence of events). The parameter values passed into the ObjectDataSource's underlying object's method can be set or customized in an event handler for the Selecting event.

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