DataGridView BindingList and CellFormatting and CellParsing

[Joe]

I have an object that inherits from BindingList<T> that I'm using as a data
source for a DataGridView. The items in the BindingList have 2 properties
which are enums. I'm using the CellParsing to assign e.Value to my enum
value and in the CellFormatting I'm doing the reverse. The problem is that
the CellFormatting e.Value is always the 1st value in the ComboBox list and
not the real value in the underlying object.

Also, dataGridView1_DataError always gets called with e.Exception =
"DataGridViewComboBoxCell value is not valid." and the Context = Formatting
| Display.

Any ideas?

For example:

enum MyEnum {Item1, Item2, Item3};

public MyClass
{
private MyEnum myenum;
private string astring;

public MyEnum TheEnum
{
get {return myenum;}
set {myenum = value;}
}

public string MyString
{
get {return astring;}
set {astring = value;}
}
}

public class MyListClass : BindingList<MyClass>
{

}

.....

DataGridViewComboBoxColumn column1 = new DataGridViewComboBoxColumn();
column1.Items.AddRange("First Item", "Second Item", "Third Item");
dataGridView1.Columns.Add(column1);

......

MyListClass listClass = new MyListClass();

dataGridView1.DataSource = listClass;

....

private void dataGridView1_CellParsing(object sender,
DataGridViewCellParsingEventArgs e)
{
if (e.DesiredType == typeof(MyEnum))
{
if (e.Value != null)
{
switch (e.Value.ToString())
{
case "First Item": e.Value = MyEnum.Item1; break;
case "Second Item": e.Value = MyEnum.Item2; break;
case "Third Item": e.Value = MyEnum.Item3; break;

}

e.ParsingApplied = true;
}
}
}

private void dataGridView1_CellFormatting(object sender,
DataGridViewCellFormattingEventArgs e)
{
// Here e.Value always equals "First Item" even after a
different item has been selected.

switch (e.ColumnIndex)
{
case 0:
if (e.Value != null && e.Value.GetType() ==
typeof(MyEnum))
{
switch ((ColumnDataFilterOperator)e.Value)
{
case MyEnum.Item1: e.Value = "First Item";
break;
case MyEnum.Item2: e.Value = "Second Item";
break;
case MyEnum.Item3: e.Value = "Third Item";
break;
}

}
}

}

Thanks for any help,
Joe

[Zhi-Xin Ye [MSFT]]

Dear Joe,

The CellParsing event occurs when a cell leaves edit mode if the cell value
has been modified.
When the form loads, none of the cells is in edit mode, so no CellParsing
event occurs, the values in the cells are still of string type, but the
desired type is MyEnum, so the "value not valid" exception throws.

For binding Enum types, then best way is calling the Enum.GetValues()
method to retrieve an array of values of the constants in a the
enumeration, then use this array as the data source of the
DataGridViewComboBoxColumn, something like this:

private void Form1_Load(object sender, EventArgs e)
{
DataGridViewComboBoxColumn column1 = new
DataGridViewComboBoxColumn();

column1.DataPropertyName = "TheEnum";
column1.DataSource = Enum.GetValues(typeof(MyEnum));

dataGridView1.Columns.Add(column1);


MyListClass listClass = new MyListClass();

listClass.Add(new MyClass("a", MyEnum.Item3));
listClass.Add(new MyClass("b", MyEnum.Item2));
listClass.Add(new MyClass("c", MyEnum.Item1));

dataGridView1.DataSource = listClass;
}

Through this approach, we can avoid the manually parsing and formatting
stuff, which means, we don't need to handle the CellParsing and
CellFormating events at all in this scenario.

[Documents for your information]

DataGridView.CellParsing Event
http://msdn.microsoft.com/en-us/library/system.windows.forms.datagridview.ce
llparsing.aspx

Enum.GetValues Method
http://msdn.microsoft.com/en-us/library/system.enum.getvalues.aspx

If you need further help on this, please don't hesitate to let me know.

Have a nice day!

Sincerely,
Zhi-Xin Ye
Microsoft Managed Newsgroup Support Team

Delighting our customers is our #1 priority. We welcome your comments and
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[Zhi-Xin Ye [MSFT]]

Dear Joe,

Does my last reply make sense to you? If you need further help, please feel
free to let me know, I will be happy to be of assistance.

Have a nice day!

Sincerely,
Zhi-Xin Ye
Microsoft Managed Newsgroup Support Team

Delighting our customers is our #1 priority. We welcome your comments and
suggestions about how we can improve the support we provide to you. Please
feel free to let my manager know what you think of the level of service
provided. You can send feedback directly to my manager at:
***@microsoft.com.

This posting is provided "AS IS" with no warranties, and confers no rights.