Correct use of casting and DataBinder.Eval

[sphengle]

It’s Friday afternoon and I’m being driven mad by a simple .NET problem. Can you help?


I’m binding in a repeater where I know there’s a possibility that the value for a field in a dataset could be null. The field is an integer.

So in ItemDataBound I’m doing this...

Int? myInt = (int?)DataBinder.Eval( Container.DataItem, “myIntField”);

This comes up with an invalid cast exception, as does this...

Int myInt = (int)DataBinder.Eval( Container.DataItem, “myIntField”);


My cop out is to do this....

String strTemp = DataBinder.Eval( Container.DataItem, “myIntField”, “{0}” ); // this returns a string

myInt = (strTemp != string.empty) ? Int.Parse( strTemp ) : 0; // or variations on this using Convert or Int.TryParse


There has to be a simpler way?

Sphengle

[Frinavale]

Since the DataBinder.Eval Method evaluates data-binding expressions at run time you will get an ArgumentNullException if the value is null (or nothing).

You're going to have to do what you have outlined above: determine if the value is null, then set it to a default value if it is null before you use the DataBinder.Eval method.

-Frinny

[sphengle]

Hi Frinny

Do you know if there is a way of testing for null without having to format to a string first?

Sphengle

[Frinavale]

Hi Frinny

Do you know if there is a way of testing for null without having to format to a string first?

Sphengle

You can use the String class's static method String.IsNullOrEmpty to check if a string is null or empty. Note that if the string contains a space, it is not null or empty...so check if it's null or empty first, then trim the string and check it again if you consider space empty as well.

-Frinny