手动添加数据源时DataGridViewComboBoxCell值出问题解决方法

给DataGridView更新数据源，采用手动方式，即首先设置手工添加不同的DataGridViewColumn。将各列DataPropertyName属性设置成数据源，就是数据库的列名或者对象名。

dataGridView1.AutoGenerateColumns = false;

DataGridViewComboBoxCell 设置的复杂一些，要设置下拉选项。参考http://technet.microsoft.com/zh-cn/library/ms404353

DataGridViewComboBoxColumn assignedToColumn = 
            new DataGridViewComboBoxColumn(); 

        // Populate the combo box drop-down list with Employee objects. 
 foreach (Employee e in employees) assignedToColumn.Items.Add(e); 

        // Add "unassigned" to the drop-down list and display it for 
        // empty AssignedTo values or when the user presses CTRL+0. 
 assignedToColumn.Items.Add("unassigned"); 
        assignedToColumn.DefaultCellStyle.NullValue = "unassigned"; 

        assignedToColumn.Name = "Assigned To"; 
        assignedToColumn.DataPropertyName = "AssignedTo"; 
        assignedToColumn.AutoComplete = true; 
        assignedToColumn.DisplayMember = "Name"; 
        assignedToColumn.ValueMember = "Self";