Does a Field exist?

[Paul]

I have a textbox bound to "Field.A".
The problem is that sometimes "Field.A" does not exist and in these cases I need to bind the textbox to "Field.B".

It was recommended that I use a user function :

public static String ResolveField()
{
string s = new string();

// ????
// Check if Field.A exists
// if yes then s = Field.A
// else s = FieldB

return s;
}

How can I check to see if a field exists without an exception?

[Steve]

Hello Paul,

Define ""Field.A" does not exist". In your example "A" is the name of your datasource column, so it should always exist. Do you mean that it might return null or a value that you want to replace with another one? You can accomplish this by using the built-in Functions like IsNull(expression, ReplacementValue) or IIf(expression, ReturnedIfTrue, ReturnedIfFalse). You can of course use an User Functions as well and handle any checks inside it with the help of your preferred language (C#, VB.NET). You would have to change the function signature to have the field as argument, and the TextBox expression should be:

= ResolveField(Fields.A)

Regards,
Steve
the Telerik team