Question

I have implemented custom control by overriding TextBox component. it has a custom property named “DbColumn”. i wanted it to act like “Name” property on TextBox, which is one Form cannot have component with same “DbColumn” value on two controls.

Is there a way to set attributes to have unique value across one Form?

Answer 1

If runtime check is enough for you, try implementing System.ComponentModel.ISupportInitialize and add checking logic to EndInit():

public class MyTextBox : TextBox, ISupportInitialize
{
     ...
     public string DbColumn { get; set; }

     public void BeginInit() { }
     public void EndInit()
     {
         bool duplicatesFound = Parent.Controls
             .OfType<MyTextBox>()
             .GroupBy(mtb => mtb.DbColumn)
             .Any(x => x.Count() > 1);

         if (duplicatesFound)
             throw InvalidOperationException("MyTextBoxes with duplicate DbColumn property found."); 
     }
}

This is pretty expensive in that form, but can be easily optimized to perform the check once for every parent container, instead of n times (for n number of MyTextBoxes).