How to check If a DataGridView column value is null or 0 in c#?

Question

I'm developing a windows form application or a books store using c#.This datagridview behave as a sales cart. Data load to datagridview from a sql database.

1st column 0,column 1,column 2,column 3, column 4 and column 5 consist with BookName, ISBN_No,Quantity,UnitPrice, Total and stock.When I select BookName, ISBN_No and Unit_price will autofill. I would like to know how to check if a datagridview cell value contains a zero or null.I tried following code. But it didn't work.

if(Convert.ToInt32(row.Cells[dataGridView1.Columns[5].Index].Value) == 0)
                {
                    MessageBox.Show("Quantiy is not Available");
                }

This didn't display anything even I enter a zero value into this datagridvie cell.

When you entered `0` what was the value of `row.Cells[dataGridView1.Columns[5].Index].Value`? `row.Cells[dataGridView1.Columns[4].Index].Value`? `row.Cells[dataGridView1.Columns[6].Index].Value`? Does https://stackoverflow.com/questions/4942593/how-to-check-if-datagridview-cell-is-null help? — mjwills, Jun 24 '18 at 21:34

score 1 · Answer 1 · answered Jun 25 '18 at 00:33

I am guessing that the awkward line of code…

Convert.ToInt32(row.Cells[dataGridView1.Columns[5].Index].Value)

may be throwing you off. The Convert.ToInt32 is going to return zero (0) if…

row.Cells[dataGridView1.Columns[5].Index].Value

returns null… therefore, using this construct is not going to help you distinguish between a null value and a zero (0) value as BOTH values will return zero (0).

The code WILL throw a FormatException exception if Value is not a valid number. It will NOT throw an exception if the value is null.

To help, I am confident you will need to break this down to three (3) parts. 1) Check for a null value. 2) If not null, check for a valid number. 3) If the number is valid, check if it is zero (0).

The “awkward” portion of the if statement is…

dataGridView1.Columns[5].Index  ???

this is “always” going to return “5”. Therefore, the statement…

Convert.ToInt32(row.Cells[dataGridView1.Columns[5].Index].Value

could be rewritten as…

Convert.ToInt32(row.Cells[5].Value

With that said, below is the code that will help distinguish between null values, non-number values and lastly if the value is zero. As Derinder suggest, using the int32.TryParse method is a better option.

private void Form1_Load(object sender, EventArgs e) {
  FillGrid();
}

private void FillGrid() {
  for (int i = 0; i < 10; i++) {
    dataGridView1.Rows.Add("C0R" + i, "C1R" + i, "C2R" + i, "C3R" + i, "C4R" + i, i);
  }
}

private void button1_Click(object sender, EventArgs e) {
  DataGridViewRow row = dataGridView1.Rows[dataGridView1.CurrentCell.RowIndex];
  if (row.Cells[5].Value != null) {
    if (Int32.TryParse(row.Cells[5].Value.ToString(), out Int32 numvalue)) {
      if (numvalue == 0) {
        MessageBox.Show("Quantity/Value is not null and is equal to zero 0");
      }
      else {
        MessageBox.Show("Quantity/Value is not null, is a valid number but it is NOT equal to zero 0. Its value is: " + numvalue);
      }
    }
    else {
      MessageBox.Show("Quantity/Value is not null but it is not a valid number. Its value is: " + row.Cells[5].Value.ToString());
    }
  }
  else {
    MessageBox.Show("Quantity/Value is null...");
  }
}

score -1 · Answer 2 · answered Jun 24 '18 at 22:30

-1

I think you can solve your Problem with "int32.TryParse" method. Other advantage is that it doesn't not throw exception like convert.toint32 ,if it doesn't succeed. You are always on safer side.

answered Jun 24 '18 at 22:30

DerInder

31
5

How to check If a DataGridView column value is null or 0 in c#?

2 Answers2