Q:

Cell with Datagridviewcombobox column displays the ValueMember instead of DisplayMember

I have a Datagridview that bounds data from database.    
 DataGridViewTextBoxColumn colOperationID = new DataGridViewTextBoxColumn();
 colOperationID.Name = "OperationID";
 colOperationID.DataPropertyName = "OperationID";
 BOMOperations.Columns.Add(colOperationID);

 DataGridViewComboBoxColumn colOperationDesc = new DataGridViewComboBoxColumn();
 colOperationDesc.Name = "OperationDesc";
 colOperationDesc.DataSource = srcDT;
 colOperationDesc.DisplayMember = "OperationDesc";
 colOperationDesc.ValueMember = "OperationID";
 colOperationDesc.DataPropertyName = "OperationDesc";
 colOperationDesc.DisplayStyle = DataGridViewComboBoxDisplayStyle.ComboBox;
 colOperationDesc.DefaultCellStyle.BackColor = Color.White;
 colOperationDesc.DisplayStyleForCurrentCellOnly = true;
 BOMOperations.Columns.Add(colOperationDesc);

Then the user will click edit button, the datagridview will become editable. My problem is when I click on datagridviewcombobox column then I will choose an item, the item will display in correctly(the DisplayMember) but as long as the cell lost focus, the cell of the combobox displays the ValueMember. 
I already tried the solution i got here to check on the datatype, but mine is corrent. The DisplayValue is a string while the DisplayValue is an int.
I tried also to change the following line colOperationDesc.DataPropertyName = "OperationDesc"; to colOperationDesc.DataPropertyName = "OperationID"; and it gives me this exception. exception

A:

colOperationDesc.DataPropertyName should be a name of the column in DataGridView.DataSource and should "refer" to same value as in colOperationDesc.ValueMember.
Notice that colOperationDesc.ValueMember and colOperationDesc.DisplayMember should be property/column names from colOperationDesc.DataSource in your case from srcDT variable.

but as long as the cell lost focus, the cell of the combobox displays
  the ValueMember

This happened because column/property "OperationDesc" (DisplayMember) not found from srcDT variable.

