Hope someone can help on this one. I have a bug in my code that I cant fix. I'm testing out using Selected Index Event handling with DataGridView control.
I have created two columns:-
Column 0 is a DataGridViewTextBoxColum
Column 1 is a DataGridViewComboBoxColumn
I have gave my ComboBox Column a Datasource that is a small DataTable consisting of two Columns which are Username & UserID.
The Display Member is set to the Username Column and I have the UserID column set as the ValueMember.
All I'm looking to do is Column 0(DataGridViewTextBox), populate with the UserID(ValueMember) on the Index Changed event for the DataGridViewComboBoxColumn.
It works fine when I first load the program. The IndexChanged Event Fires without any error. But if I try to select the ComboBox in the new row, it is clearing the value in combobox from the previous row, and then throwing a Null Reference Exception.
I have listed the Code Below and Highlighted the line of the code that it fails at :-
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
LoadData();
}
public OleDbConnection con = new OleDbConnection(@"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\Documents and Settings\riversd\Desktop\Test.accdb");
public string sql = "SELECT * FROM [AgentList]";
private void LoadData()
{
dataGridView1.EditMode = DataGridViewEditMode.EditOnEnter;
DataTable dt = AgentTable(sql, con);
DataGridViewTextBoxColumn textbox = new DataGridViewTextBoxColumn();
dataGridView1.Columns.Add(textbox);
DataGridViewComboBoxColumn combo = new DataGridViewComboBoxColumn();
combo.DataSource = dt;
combo.DisplayMember = "agentName";
combo.ValueMember = "AgentID";
dataGridView1.Columns.Add(combo);
}
public DataTable AgentTable(string SQL, OleDbConnection con)
{
var AgentList = new DataTable();
var SELECTcommand = new OleDbCommand(SQL, con);
var adaptor = new OleDbDataAdapter();
adaptor.SelectCommand = SELECTcommand;
con.Open();
adaptor.SelectCommand.ExecuteNonQuery();
adaptor.Fill(AgentList);
con.Close();
return AgentList;
}
private void dataGridView1_CurrentCellDirtyStateChanged(object sender, EventArgs e)
{
DataGridViewColumn col = dataGridView1.Columns[dataGridView1.CurrentCell.ColumnIndex];
if (col is DataGridViewComboBoxColumn)
{
dataGridView1.CommitEdit(DataGridViewDataErrorContexts.Commit);
}
}
private void dataGridView1_EditingControlShowing(object sender, DataGridViewEditingControlShowingEventArgs e)
{
if (dataGridView1.CurrentCell.ColumnIndex == 1 && e.Control is ComboBox)
{
ComboBox comboBox = e.Control as ComboBox;
comboBox.SelectedIndexChanged += LastColumnComboSelectionChanged;
}
}
private void LastColumnComboSelectionChanged(object sender, EventArgs e)
{
var currentcell = dataGridView1.CurrentCellAddress;
var sendingCB = sender as DataGridViewComboBoxEditingControl;
DataGridViewTextBoxCell cel = (DataGridViewTextBoxCell)dataGridView1.Rows[currentcell.Y].Cells[0];
// HERE IS THE LINE THAT THROES EXCEPTION WHEN MOVING FROM
// ONE COMBOXCELL to another.
cel.Value = sendingCB.SelectedValue.ToString();
}
}
