You are creating a Windows Forms application by using the .NET Framework 3.5.You write the following code segment to bind a list of categories to a dropdown list.（Line numbers are included for reference only.）

You need to ensure that the dropdown list meets the following requirements： 
（1）Displays all category names  
（2）Uses the category ID as the selected item value   
Which code segment should you add at line 06？（）

 

You are creating a Windows Forms application by using the .NET Framework 3.5. You plan to modify a list of orders within a DataGridView control in the application. You need to ensure that a value is required in the first column of the grid control. 
Which code segment should you use？（）