Generating Combo Box in DataGrid Columns

DataGrid programming in .NET is real fun. And that too if youre trying to get it programmed in a Windows Forms world its double the work. You got to write a whole lot of code for a simple extensibility of the existing features of datagrid. One good example is having a combobox in one of the columns of the datagrid.  

A week ago, I needed this feature in one of my assignments. I thought I could grab a couple of clues/lines of code from the documentation. But I couldn't find one. I then posted my requirement at the list and one of the guys over the list pointed me to a sample ( that is written in VB.NET.  

I sat down to port this code into C#. And I also took time in adding couple more features like Updating the changes made in the grid and moving between records. 

The sample uses the SQLServer database. You got to change the connection string to your appropriate database. The tables I am using are 

Table                Columns
Students            Sno(PK), SName, Course(Foreign Key)

Course              Course(PK) (Combo Box populates these rows). 

I generate a dataset named _StudentDS which is populated with data from both the tables.  

sqlDA.Fill(_StudentDS, "Course"); 

The .zip file consists of  

If you make any changes, I would appreciate if you send me your piece of work. 

Form2 The form that encapsulates code for the datagrid with combobox as one of its columns and the necessary operations.

SjComboboxDataGrid is the component thata contains two classes

(a)    DataGridCombobox, this derives from Combobox class.

(b)    DataGridComboboxColumn this derives from DataGridColumnStyle, which is an abstract class, which specifies the appearance and text formatting, and behavior of a DataGrid control.  

When you bind a datagrid to a datasource, the datagrid control automatically creates a collection of DataGridColumnStyle objects. The objects created are actually instantiations of one of the DataGridBoolColumn or DataGridTextBox classes that inherit from DataGridColumnStyle. This done by the datagrid by checking the datatype of the datacolumn its trying to populate using the GetType( ) method. 

You can also create your own set of DataGridColumnStyle objects like the one I did in the example which has a combo box in it. When you inherit from DataGridColumnStyle you must override these members Abort, Commit, Edit and Paint(twice). You must set the MappingName of each column style to the ColumnName of a DataColumn to synchronize the display of columns with actual data. 

GridTableStyle.MappingName = "Student";
_CourseDT = _StudentDS.Tables["Course"]; 

Binding an ordinary column to a DataGridColumnStyle column
GridTableStyle.GridColumnStyles.Add(new DataGridTextBoxColumn(objStudentCM .GetItemProperties()["SNo"]));
GridTableStyle.GridColumnStyles[0].MappingName = "SNo";
GridTableStyle.GridColumnStyles[0].HeaderText = "Student No";
GridTableStyle.GridColumnStyles[0].Alignment = HorizontalAlignment.Left;
GridTableStyle.GridColumnStyles[0].NullText = string.Empty;


Binding data to a combobox style column
GridTableStyle.GridColumnStyles.Add(new DataGridComboBoxColumn(_CourseDT,0,0));
GridTableStyle.GridColumnStyles[2].MappingName = "Course";
GridTableStyle.GridColumnStyles[2].HeaderText = "Course";
GridTableStyle.GridColumnStyles[2].Alignment = HorizontalAlignment.Left;
GridTableStyle.GridColumnStyles[2].Width = IntAvgCharWidth * 20;
GridTableStyle.GridColumnStyles[2].NullText = string.Empty; 

Enjoy the code.