Ummm...I'm know it seems like it should be obvious, but what does this mean:

Type 'System.Web.UI.WebControls.DataKey' in Assembly 'System.Web, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' is not marked as serializable.

You need to put [Serializable] above the procedure signature. Why? Depends on what you're writing and how/why.

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