http://www.cnblogs.com/LifeKingcn/archive/2012/08/21/2649380.html
1. 首先在初始化Gridview时候定义主键的数组。
GridViewTeacherStudent.DataKeyNames=new string[] {"courseId","studentId","type","level","unit"};2. 在进行删除操作，或者对某行进行操作获得列中的值。
string studentId = GridViewTeacherStudent.DataKeys[e.RowIndex]["studentId"].ToString().Trim();3.如果只有单个的键值时候。如只有”StudentId“一个主键下面直接获得。
string studentId = GridViewTeacherStudent.DataKeys[e.RowIndex].Value.ToString().Trim();
在 GridView1_RowCommand中获取主键的值：
protected void GridView1_RowCommand(object sender, GridViewCommandEventArgs e)
{
int OrderId = Convert.ToInt32(GridView1.DataKeys[Convert.ToInt32(e.CommandArgument)].Value);
}在 GridView1_PageIndexChanging中获取主键的值
protected void GridView1_PageIndexChanging(object sender, GridViewPageEventArgs e)
{
int index=GridView1.DataKeys[e.NewPageIndex].Value;
}在 GridView1_RowDeleting中获取主键的值
protected void GridView1_RowDeleting(object sender, GridViewDeleteEventArgs e)
{
int index=GridView1.DataKeys[e.RowIndex].Value;
}在 GridView1_RowEditing中获取主键的值
protected void GridView1_RowEditing(object sender, GridViewEditEventArgs e)
{
int index = GridView1.DataKeys[e.NewEditIndex].Value;
}在 GridView1_RowUpdating中获取主键的值
protected void GridView1_RowUpdating(object sender, GridViewUpdateEventArgs e)
{
int index = GridView1.DataKeys[e.RowIndex].Value;
}在 GridView1_RowDataBound中获取主键的值
protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)
{
int index = GridView1.DataKeys[e.Row.RowIndex].Value;
}