DataGridView ComboBoxCell, ArgumentExcepti on

[preeethi]

Hello,

I'm designing a DataGridView that has a few combobox columns.

As the user selects a value from a ComboBoxCell in a row. I want to populate another ComboBoxCell in the same row with the corresponding dataset.

for eg:
step1: ComboBoxCell1 - Items: Categories
[Authors: "Ayn Rand", "George Orwell", "Joseph Heller" etc...]
step2: ComboBoxCell2 Items: Members of the selected Categories in step1.
[Books by "Ayn Rand": "Fountain Head","Atlas Shrugged", etc...]

Length of the Members varies in each Category.

ComboBoxCell doesn't allow me to assign values. I can ONLY add to the Items and cannot clear/edit them. If I do, I get System.Argument Exception.

I tried, to set a DataSource<a datatable> to this column and change the DisplayMembers each time the category changes for a row. I have two problems in this approach:
1. Table's Column length with non-null values are variable. So the combobox displays a few Items with null values as the case may be.
2. Everytime the category changes, I <again> get the System.Argument Exception.

The way am doing this is:
Approach 1:
---On cell value change:
DataGridViewCom boBoxCell combocell = (DataGridViewCo mboBoxCell) MyDataGridView[column,row];
combocell.Items .Clear(); [throws argument exception]
combocell.AddRa nge(<values>);

or

Approach 2:
DataGridViewCom boBoxColumn MyColumn = new DataGridViewCom boBoxColumn();
MyColumn.DataSo urce = MyDataTable;
---On cell value change:
combocell.Displ ayMember = "ColumnName "; (from MyDataTable)
(throws ArgumentExcepti on anytime DisplayMember is re-assigned)

I'd appreciate any help I can get.

Thanks,
Preethi

[preeethi]

To enable this, two versions of the filtered list (subcategory) need to be created.

Heres how I did it:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
 
namespace DataGridProblem
{
  public partial class Form1 : Form
  {
    DataTable categoryDT, subCategoryDT;
    BindingSource catBS, filteredSubCatBS, unfilteredSubCatBS;    
 
    public Form1()
    {
      categoryDT = new DataTable("category");
      categoryDT.Columns.Add("ID", typeof(int));
      categoryDT.Columns.Add("Name", typeof(string));
 
      subCategoryDT = new DataTable("subcategory");
      subCategoryDT.Columns.Add("ID", typeof(int));
      subCategoryDT.Columns.Add("subID", typeof(int));
      subCategoryDT.Columns.Add("Name", typeof(string));
 
      categoryDT.Rows.Add(new object[] { 0, "cat0" });
      categoryDT.Rows.Add(new object[] { 1, "cat1" });
      categoryDT.Rows.Add(new object[] { 2, "cat2" });
 
      subCategoryDT.Rows.Add(new object[] { 0, 0, "SubCat0-Cat0" });
      subCategoryDT.Rows.Add(new object[] { 1, 0, "SubCat1-Cat0" });
      subCategoryDT.Rows.Add(new object[] { 2, 0, "SubCat2-Cat0" });
      subCategoryDT.Rows.Add(new object[] { 3, 1, "SubCat3-Cat1" });
      subCategoryDT.Rows.Add(new object[] { 4, 1, "SubCat4-Cat1" });
      subCategoryDT.Rows.Add(new object[] { 5, 1, "SubCat5-Cat1" });
      subCategoryDT.Rows.Add(new object[] { 6, 2, "SubCat6-Cat2" });
      subCategoryDT.Rows.Add(new object[] { 7, 2, "SubCat7-Cat2" });
      subCategoryDT.Rows.Add(new object[] { 8, 2, "SubCat8-Cat2" });
 
      InitializeComponent();
 
      catBS = new BindingSource();
      catBS.DataSource = categoryDT;
 
      CategoryCol.DataSource = catBS;
      CategoryCol.DisplayMember = "Name";
      CategoryCol.ValueMember = "ID";
 
      // the ComboBox column is bound to the unfiltered DataView
      unfilteredSubCatBS = new BindingSource();
      DataView undv = new DataView(subCategoryDT);
      unfilteredSubCatBS.DataSource = undv;
 
      SubCategoryCol.DataSource = unfilteredSubCatBS;
      SubCategoryCol.DisplayMember = "Name";
      SubCategoryCol.ValueMember = "ID";
 
      // this binding source is where I perform my filtered view
      filteredSubCatBS = new BindingSource();
      DataView dv = new DataView(subCategoryDT);
      filteredSubCatBS.DataSource = dv;
 
    }
 
    private void dataGridView1_CellBeginEdit(object sender, DataGridViewCellCancelEventArgs e)
    {
      try 
      {
        if (e.ColumnIndex == SubCategoryCol.Index)
        {
          DataGridViewComboBoxCell dgcb = (DataGridViewComboBoxCell)dataGridView1[e.ColumnIndex, e.RowIndex];
          dgcb.DataSource = filteredSubCatBS;
          this.filteredSubCatBS.Filter = "subID = " + this.dataGridView1[e.ColumnIndex - 1, e.RowIndex].Value.ToString();          
        }      
      }
      catch (Exception ex)
      {
        MessageBox.Show(ex.Message + ex.StackTrace);
      }
    }
 
    private void dataGridView1_CellEndEdit(object sender, DataGridViewCellEventArgs e)
    {
      try
      {
        if (e.ColumnIndex == SubCategoryCol.Index)
        {
          DataGridViewComboBoxCell dgcb = (DataGridViewComboBoxCell)dataGridView1[e.ColumnIndex, e.RowIndex];
          dgcb.DataSource = unfilteredSubCatBS;
          this.filteredSubCatBS.RemoveFilter();
        }
      }
 
      catch (Exception ex)
      {
        MessageBox.Show(ex.Message + ex.StackTrace);
      }      
    }
  }
}