Object reference not set to an instance of an object

Keerthika Reddy

private void GetColumns(string key, DataGridView dataGrid)

{

string strQuery = string.Format("select col_index, col_name, display_name, col_type, visible, col_width from rayonpos.datagridcolumns where source_key = '{0}' order by col_index", key);

DataTable dtColumns = DataService.ExecuteQueryAndReturnTable(strQuery);

if (dtColumns.Rows.Count > 0)

{

dataGrid.Columns.Clear();

foreach (DataRow dtRow in dtColumns.Rows)

{

DataGridViewColumn dgvCol = null;

if (dtRow["col_type"].ToString().ToUpper() == "TEXT")

{

dgvCol = new DataGridViewTextBoxColumn();

}

dgvCol.Name = dtRow["col_name"].ToString();

dgvCol.HeaderText = dtRow["display_name"].ToString();

dgvCol.Visible = Convert.ToBoolean(dtRow["visible"]);

dgvCol.Width = Convert.ToInt16(dtRow["col_width"]);

dataGrid.Columns.Insert(Convert.ToInt16(dtRow["col_index"]), dgvCol);

}

3 Replies

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Roshan Patil7y ago
In your code after the foreach loop, you are setting the DataGridViewColumn variable dgvCol to null.

foreach (DataRow dtRow in dtColumns.Rows)
{
DataGridViewColumn dgvCol = null;

Post this if your IF condition fails, i.e. col_type is not 'TEXT' the n execution goes to the red and yellow hilighted line.

if (dtRow["col_type"].ToString().ToUpper() == "TEXT") //fails
{
dgvCol = new DataGridViewTextBoxColumn();
}
dgvCol.Name = dtRow["col_name"].ToString();

as the value of this DataGridViewCoumn variable dgvCol is not yet initalized to anything, it cannot have a Name property (dgvCol.Name). Hence at runtime an error of invalid Object reference will be raised (As the object for DataGridViewCoumn is not yet initialized).
Rajkiran Swain7y ago
Most of the time, when you try to assing value into object, and if the value is null, then this kind of exception occur.
Amit Gupta7y ago
There might be null value, you can yry like this dgvCol.Name = dtRow["col_name"] +"";