C# :: Grid Column To Always Have 0 Or Change Error Message

Basically I wanna make my textbox to contain only positive numbers. I was able to do that via masking and regex. I should let you know that the column is bound to a variable which is an int. Therefore, the user always have to type an int (no letters or characters). Like I said, I have been able to prevent user from typing anything but numbers.

Now to the problem:When the user leaves the cell blank and chooses to get out of that cell, they'd get "Input string was not in correct format" next to that cell.

-My approach is: whenever there is nothing in the cell, just replace it with 0. I have code that I thought will do that, but it wont. Seems like the cell was not null, because the if clause won't execute. This is the code:

private void gridView1_CellValueChanged(object sender, DevExpress.XtraGrid.Views.Base.CellValueChangedEventArgs e) {
GridView view = sender as GridView;
if ((view.GetRowCellValue(e.RowHandle, colPriority).ToString() == "") ) {
list.ElementAt(this.gridView1.FocusedRowHandle).priority = 0;
}
}

-Another approach is to change the display or the error message to like "Please enter a number." I have tried doing this but no luck. When I try this concept with the code below, it pops me a dialog box say "Do you wanna change the value?". I dont want it to pop up a dialog box. Also, i was looking for a message that I tried to give it. Looks like it doesn't even get in the if clause because I have checked. And its because its not null? I dont know. This is the code:

private void gridView1_ValidateRow(object sender, DevExpress.XtraGrid.Views.Base.ValidateRowEventArgs e) {
GridView view = sender as GridView;
GridColumn priority = view.Columns["Priority"];
if (view.GetRowCellValue(e.RowHandle, colPriority) == null) {
e.Valid = false;
//Set errors with specific descriptions for the columns
view.SetColumnError(colPriority, "Incorrect Value");
}
}

PS:I have checked that both of these methods get executed, so it isn't like they don't. I used some console.write stuff to check this.