ASP.NET Convert Invalid String to Null

Question

In my application I have TextBox in a FormView bound to a LinqDataSource like so:

<asp:TextBox ID="MyTextBox" runat="server" 
             Text='<%# Bind("MyValue") %>' AutoPostBack="True" 
             ontextchanged="MyTextBox_TextChanged" />

protected void MyTextBox_TextChanged(object sender, EventArgs e)
{
    MyFormView.UpdateItem(false);
}

This is inside an UpdatePanel so any change to the field is immediately persisted. Also, the value of MyValue is decimal?. This works fine unless I enter any string which cannot be converted to decimal into the field. In that case, the UpdateItem call throws:

LinqDataSourceValidationException - Failed to set one or more properties on type MyType. asdf is not a valid value for Decimal.

I understand the problem, ASP.NET does not know how to convert from 'asdf' to decimal?. What I would like it to do is convert all these invalid values to null. What is the best way to do this?

Answer 1

I think you should handle the Updating event of the LinqDataSource on your page. Do your check for invalid strings (use a TryParse method or something), and then continue with the base class update.

(Edit: My intuition lines up with what's recommended here)

Answer 2

Not familiar with ASP, but in .net, couldn't you just do something along the lines of

protected void MyTextBox_TextChanged(object sender, EventArgs e)
{ 
    Decimal d = null;
    TextBox tb = sender as TextBox;

    if(!Decimal.TryParse(tb.Text, out d))
    {
            tb.Text = String.Empty;
    }
    MyFormView.UpdateItem(false);
}