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Expression. DivideByZeroException.

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This is a migrated thread and some comments may be shown as answers.
Dominik
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Dominik asked on 25 Jun 2013, 10:58 AM
Hi,

To reproduce problem just add 3 columns to grid and paste code below to Load event.

private void Form1_Load(object sender, EventArgs e)
{
    DataTable dt = new DataTable();
    dt.Columns.Add("d1", typeof(Decimal));
    dt.Columns.Add("d2", typeof(Decimal));
 
    dt.Rows.Add(new object[] { 3, 4 });
    dt.Rows.Add(new object[] { 1, 4 });
    dt.Rows.Add(new object[] { 0, 3 });
    dt.Rows.Add(new object[] { 3, 3 });
 
    radGridView1.Columns[0].FieldName = "d1";
    radGridView1.Columns[0].HeaderText = "d1";
    radGridView1.Columns[0].Name = "d1";
 
    radGridView1.Columns[1].FieldName = "d2";
    radGridView1.Columns[1].HeaderText = "d2";
    radGridView1.Columns[1].Name = "d2";
 
    radGridView1.Columns[2].HeaderText = "exp";
 
    radGridView1.DataSource = dt;
 
    radGridView1.Columns[2].Expression = "IIF(d1 = 0, 0, d2 / d1 )";
}

Even if we apply the condition that checks divide by zero, program will trow error:
A first chance exception of type 'System.DivideByZeroException' occurred in mscorlib.dll 

I was able to fool the "Expression" by double condition like this:

radGridView1.Columns[2].Expression = "IIF(d1 = 0, 0, d2 / (IIF(d1 = 0, 9999 , d1)))";




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Maarten
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answered on 25 Jun 2013, 02:04 PM
Hi,

If possible, you should use a Case, like 

"CASE WHEN d1 = 0 THEN 0 ELSE d2 / d1 END"

IIF always evaluates both sides.

Cheers
Maarten
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Dimitar
Telerik team
answered on 25 Jun 2013, 05:52 PM
Hi Dominik,

Thank you for writing.

To avoid the described behavior you can create a custom function like this:
public class CustomExpressionContext : Telerik.Data.Expressions.ExpressionContext
{
    /// <summary>
    /// My custom function, 
    /// </summary>
    /// <returns></returns>
    public decimal CustomDivide(decimal d1, decimal d2)
    {
        if (d1 == 0m)
        {
            return 0m;
        }
        else
        {
            return d2 / d1;
        }
    }
}

Then attach the function in the expression string like this:

Telerik.Data.Expressions.ExpressionContext.Context = new CustomExpressionContext();
this.radGridView1.Columns[2].Expression = "CustomDivide(d1, d2)"

I hope this helps. Should you have any other questions do not hesitate to ask. Regards,
Mitko
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