怎么在GridView中动态添加复选框（GridView用代码创建） .

 private GridView CreateTextBox()
        {
            GridView freeTextBox = new GridView();
            freeTextBox.Width = new Unit(1000);
            freeTextBox.Height = new Unit(600);

            BoundField bf1 = new BoundField();
            BoundField bf2 = new BoundField();
            BoundField bf3 = new BoundField();
            BoundField bf4 = new BoundField();
            BoundField bf5 = new BoundField();

            bf1.HeaderText = "姓名";
            bf1.DataField = "stuName";
            bf1.ReadOnly = true;
            bf1.SortExpression = "stuName";

            bf2.HeaderText = "性别";
            bf2.DataField = "stuSex";
            bf2.SortExpression = "stuSex";

            bf3.HeaderText = "电话";
            bf3.DataField = "stuPhone";
            bf3.SortExpression = "stuPhone";

            bf4.HeaderText = "生日";
            bf4.DataField = "stuBirthday";
            bf4.SortExpression = "stuBirthday";

            bf5.HeaderText = "地址";
            bf5.DataField = "stuAddress";
            bf5.SortExpression = "stuAddress";

            freeTextBox.Columns.Add(bf1);
            freeTextBox.Columns.Add(bf2);
            freeTextBox.Columns.Add(bf3);
            freeTextBox.Columns.Add(bf4);
            freeTextBox.Columns.Add(bf5);
        
           //如何添加复选框

            freeTextBox.EditIndex = -1;

            freeTextBox.AutoGenerateEditButton = true;
            freeTextBox.RowCancelingEdit += new GridViewCancelEditEventHandler(formtextbox_RowCancelingEdit);
            freeTextBox.RowEditing += new GridViewEditEventHandler(formtextbox_RowEditing);
            freeTextBox.RowUpdating += new GridViewUpdateEventHandler(formtextbox_RowUpdating);//********


          freeTextBox.AutoGenerateColumns = false;

           return freeTextBox;
        }

CheckBoxField

------解决方案--------------------
帮顶一下！！