Convert.ToInt throws Object cannot be cast from DBNull to other types

Question

What seems to be wrong with the below code? I think there are null in the database, how do I sum a column that contains null?

int Total_QtyinHand = 0;
int Total_QtyAllocated = 0;
int Total_QtyinStock = 0;
int Total_QtyUpcoming = 0;

protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)
{
    if (e.Row.RowType == DataControlRowType.DataRow)
    {
        // VVV  --- Exception happens on the line below --- VVV
        Total_QtyinHand += Convert.ToInt32(DataBinder.Eval(e.Row.DataItem, "QuantityonHand"));
        Total_QtyAllocated += Convert.ToInt32(DataBinder.Eval(e.Row.DataItem, "Allocated_Quantity"));
        Total_QtyinStock += Convert.ToInt32(DataBinder.Eval(e.Row.DataItem, "Qty_in_Stock"));
        Total_QtyUpcoming += Convert.ToInt32(DataBinder.Eval(e.Row.DataItem, "UpcomingStock"));
    }

    else if (e.Row.RowType == DataControlRowType.Footer)
    {
        e.Row.Cells[3].Text = "Total Qty";
        e.Row.Cells[3].Font.Bold = true;

        e.Row.Cells[4].Text = Total_QtyinHand.ToString();
        e.Row.Cells[4].Font.Bold = true;

        e.Row.Cells[5].Text = Total_QtyAllocated.ToString();
        e.Row.Cells[5].Font.Bold = true;

        e.Row.Cells[6].Text = Total_QtyUpcoming.ToString();
        e.Row.Cells[6].Font.Bold = true;
    }

}

Try this way http://stackoverflow.com/questions/2433155/handle-dbnull-in-c-sharp — Mitja, Dec 24 '14 at 09:16
This line throws the exception Total_QtyinHand += Convert.ToInt32(DataBinder.Eval(e.Row.DataItem, "QuantityonHand")); — Sales QOrbit, Dec 24 '14 at 09:16
Why not use TryParse ? int outValue = 0; int.TryParse(DataBinder.Eval(e.Row.DataItem, "QuantityonHand"), out outValue); Total_QtyinHand += outValue; — barca_d, Dec 24 '14 at 09:20

senthilkumar2185 · Answer 1 · 2014-12-24T11:26:18.317

-1

this code working fine in my test

tot += DataBinder.Eval(e.Row.DataItem, "mylab").ToString() != string.Empty 
    ? Convert.ToInt32(DataBinder.Eval(e.Row.DataItem, "mylab")) 
    : 0;

e.Row.Cells[0].Text = tot.ToString();

edited Dec 24 '14 at 11:26

answered Dec 24 '14 at 09:21

senthilkumar2185

2,536
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And of course, the DataBinder.Eval(e.Row.DataItem, "QuantityonHand") could well be extracted to a variable because it makes the code so unreadable this way – barca_d Dec 24 '14 at 09:23
!String.isnullorEmpty(DataBinder.Eval(e.Row.DataItem, "QuantityonHand").Tostring() ) then try – senthilkumar2185 Dec 24 '14 at 10:24
you is bad you also convert to object that also bad idea y u accept – senthilkumar2185 Dec 24 '14 at 11:03
I downvoted this question for a couple of reasons: The double call to `DataBinder.Eval` which is pretty expensive, the comparison to `null` which won't work, since the DataBinder is returning `DBNull.Value` and the expensive string conversion, which is the wrong solution to the problem (even though it works). Finally: there is no explanation on why this works and what was wrong in the first place. – jessehouwing Dec 24 '14 at 11:24

jessehouwing · Accepted Answer · 2014-12-25T11:31:49.573

When using the database API, a value will be substituted with DBNull.Value in case of a null value in the database. Your code tries to directly convert that to an int which fails. Comparing the value directly to null doesn't help either, as the value is not null, but DBNull.Value.

So:

object value = DataBinder.Eval(e.Row.DataItem, "QuantityonHand");
if (value != DBNull.Value) { Total_QtyinHand += (int)value; }

Or if the value is actually a string under the hood, you may need to parse it instead. It's better to upgrade the schema of your database to actually store and return a numeric value though, more on that later:

object value = DataBinder.Eval(e.Row.DataItem, "QuantityonHand");
if (value != DBNull.Value)
{ 
    int result = -1;
    if (int.TryParse((string)value, NumberStyles.Integer, CultureInfo.InvariantCulture, out result))
    {
       Total_QtyinHand += result;
    }
}

You can of course capture this logic in a separate function, or play around with the ?: operator:

object value = DataBinder.Eval(e.Row.DataItem, "QuantityonHand");
Total_QtyinHand += (value == DBNull.Value ? 0 : (int)value);

While researching answers, you might find a lot of suggestions to round-trip the value through a string and parse it again. This can lead to very strange behavior and I strongly suggest not to do that. I've even written an FxCoprule in the past to catch these buggers in the code. The value in the database is already a numeric format if your schema is correct and there should be no reason to introduce all kinds of freaky behavior with Culture parsing sand such. When using a .Parse or .TryParse method, make sure you supply it with the expected NumberStyle and the culture the number is stored in to prevent accidental parse mistakes (like multiplying the value by 100 if the decimal separator is set incorrectly).

What's the purpose of giving an answer to a duplicate and a _Please help!_ question? You've eddited the question and didn't remove the phrase too and still you've 20k rep :-\ — t3chb0t, Dec 25 '14 at 12:39

Convert.ToInt throws Object cannot be cast from DBNull to other types

2 Answers2