I'd like to do some custom validation in a Dynamic Data ENTITY FRAMEWORK application similar to the following:-

if (ForeignKeyField = "A") { if (TextFieldA = "") { show error 'you must enter a value for field A'  } }

if (ForeignKeyField = "B") { if (TextFieldB = "") { show error 'you must enter a value for field B'  } }

if (ForeignKeyField = "C") { if (TextFieldC = "") { show error 'you must enter a value for field C'  } }

Can anyone point me in the right direction with links to existing examples or sample code ?

Thanks in Advance !

If I understand your question correctly, you can already do this by annotating your model using RequiredAttribute (note, you can customize the error message using the attribute's properties). Read How to: Customize Data Field Validation in the Data Model for a walkthrough.

If this does no address your scenario, please clarify what you are trying to do.