Here Mudassar Ahmed Khan has provided solution to the following exception (error) which occurs when adding a Default (Blank) Item to ComboBox after it is populated with some DataSource in Windows Forms (WinForms) Application using C# and VB.Net.

Items collection cannot be modified when the DataSource property is set.

Here Mudassar Ahmed Khan has explained with an example, how to Filter DataGridView using ComboBox in Windows Forms Application using C# and VB.Net.

By default the DataGridView will show all records. As soon as user selects an item in ComboBox, the records will be searched in Database and the DataGridView rows will be filtered in Windows Forms (WinForms) Application using C# and VB.Net.

Here Mudassar Ahmed Khan has explained with an example, how to add (insert) Default First Value (Item) in ComboBox (DropDownList) in Windows Forms Application using C# and VB.Net.

First a DataTable will be populated from database and then the Default First Value (Item) will be added to it, finally the ComboBox will be populated from DataTable in Windows Forms Application using C# and VB.Net.

Here Mudassar Ahmed Khan has explained with an example, how to bind (populate) ComboBox from Database using DataTable (DataSet) in Windows Forms using C# and VB.Net.