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
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