Overwriting ControlParameters of DataSources in code-behind

I have an ObjectDataSource (but perhaps this question is the same for all kinds of DataSources which support parameter collections):

<asp:ObjectDataSource ID="MyObjectDataSource" runat="server" 
    TypeName="MyData"
    OldValuesParameterFormatString="original_{0}" 
    SelectMethod="GetMyData" >
    <SelectParameters>
        <asp:ControlParameter ControlID="MyTextBox" Name="MyParameter" Type="String" />
    </SelectParameters>
</a开发者_开发知识库sp:ObjectDataSource>

As you can see there is a ControlParameter bound to a TextBox on the aspx page. So the content of this TextBox is a parameter for my SelectMethod. But there is a special button on the page: When this button is clicked and a postback occurs I don't want that the DataSource extracts the content of the TextBox to control the selection, instead I want to set a specific hard value "x" as the selection parameter.

How can I do that? Can I "disable" in some way the ControlParameter when this specific button is clicked and set my special value instead? Or is there any other way?

Thank you for feedback in advance!

I've found this solution myself:

I've replaced the asp:ControlParameter by a "generic" parameter:

<SelectParameters>
    <asp:Parameter Name="MyParameter" Type="String" />
</SelectParameters>

...and then in the event handler for the special button:

MyObjectDataSource.SelectParameters["MyParameter"].DefaultValue = "x";

In the event handler of the button which shall run the selection by the TextBox content:

MyObjectDataSource.SelectParameters["MyParameter"].DefaultValue = MyTextBox.Text;

I don't know if this is a good solution or if it can have unwished side effects. But at the moment it works. (I was wondering anyway what's the purpose of "generic" parameters. Perhaps exactly this: "Unbound" parameters to be set only by code-behind (aside from being the base class of customized parameter classes)).