Object reference not set to an instance of an object.

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hi every body i have agridview where i need to fill all row coloumn from one of the column when i open the form and before moving to the column where i will put data and the other column binnding from it i get the following error NullReferenceException (Object reference not set to an instance of an object)
my code is

C#

private void Form_Load(object sender, EventArgs e)
      {
          this.dataGridView1.CellValidated += new DataGridViewCellEventHandler(dataGridView1_CellValidated);

          dataGridView1.RowPostPaint += dataGridView1_RowPostPaint;


      }

   private void dataGridView1_CellValidated(object sender, DataGridViewCellEventArgs e)
      {
          int count = dataGridView1.Columns.Count;


          if (e.RowIndex >= 0)
          {
              if (!string.IsNullOrEmpty(dataGridView1.Rows[e.RowIndex].Cells["txtproname"].Value.ToString()))
              {
                  _id1 = dataGridView1.Rows[e.RowIndex].Cells["txtproname"].Value.ToString();
                  PopulateColumns();
                  dataGridView1.Rows[e.RowIndex].Cells[3].Value = _barcode;
                  dataGridView1.Rows[e.RowIndex].Cells[4].Value = _price;
                  dataGridView1.Rows[e.RowIndex].Cells[5].Value = _unit;
              }
          }

      }

the error gets here
if (!string.IsNullOrEmpty(dataGridView1.Rows[e.RowIndex].Cells["txtproname"].Value.ToString()))

how can i be solved?? need help

Posted 16-May-15 0:11am

ost3z

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Sascha Lefèvre · Accepted Answer · 2015-05-16T00:25:00

Solution 1

The idea of using String.IsNullOrEmpty(..) is alright - but before this method does its checking, you access the potentially "null-containing" property .Value with .ToString().

If the cell can only contain a String or null, then replace it with a simple cast to String and it'll work (or, at least it won't cause the exception any more):

C#

if (!string.IsNullOrEmpty((string)dataGridView1.Rows[e.RowIndex].Cells["txtproname"].Value))

If the cell can contain contain something else than a string or null, then it's just a tiny bit more complex:

C#

object cellValue = dataGridView1.Rows[e.RowIndex].Cells["txtproname"].Value;
if (cellValue != null && !string.IsEmpty(cellValue.ToString()))

Posted 16-May-15 0:25am

Sascha Lefèvre

Updated 16-May-15 0:46am

v5

Comments

Maciej Los 16-May-15 6:27am

Sounds perfectly ;)

Sascha Lefèvre 16-May-15 6:39am

Actually it wasn't quite, *cough*, but now it should be ;-)

ost3z 16-May-15 8:48am

thank you too much it worked fine but there is aproblem happened with my combox the value get clear on living the cell
private void dataGridView1_EditingControlShowing(object sender, DataGridViewEditingControlShowingEventArgs e)
{

string titleText = dataGridView1.Columns[2].HeaderText;
if (titleText.Equals("proname"))
{
ComboBox cbo = e.Control as ComboBox;
if (cbo != null)
{
cbo.DropDownStyle = ComboBoxStyle.DropDown;
cbo.AutoCompleteMode = AutoCompleteMode.SuggestAppend;
cbo.AutoCompleteCustomSource = AutoCompleteLoad();
cbo.AutoCompleteSource = AutoCompleteSource.CustomSource;
}
}

}

thank again for helping

Sascha Lefèvre 16-May-15 9:09am

You're welcome! Glad I could help :)

But unfortunately I can't help you with this follow-up problem. Please post it as a new question so someone else can help you there :)