Databinding NULL Value To A Checkbox

Posted on 2006-06-30
Medium Priority
Last Modified: 2012-08-13
The Following line works if the value in the database is a 0 or 1
      chkCrown.DataBindings.Add("Checked", dsPipeline, "PipelineDS.Crown")

If a NULL is present then I get:
Object cannot be cast from DBNull to other types.
which seems reasonable.  

I would like the checkbox to go to an
Indeterminate checkstate if a NULL is encountered.  How would I do this?


Question by:nebbles
LVL 34

Accepted Solution

Sancler earned 1600 total points
ID: 17021326
You could

1)  if your database supports it, include in IIF clause in your SELECT statement to bring over a value of 2 if the actual value is Null.  Then you could bind "CheckState" to the column.

2)  add an expression column to your datatable containing an IIF to return 2 if the actual value is Null.  You could then bind "CheckState" to that expression column.

3)  add handlers to the binding for its .Format and .Parse events and convert Null to 2 in the .Format code and convert 2 back to Null in the .Parse code.  Again, the binding would have to be to "CheckState" but it couldbe on the "raw" column.


Expert Comment

ID: 17022220
you could try this out...

SELECT ISNULL(Crown, 0) AS Crown FROM PipelineDS ... in your sql statement.

This will set your checkbox state to unchecked if it is <NULL>.

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