How to edit rows in gridview in ASP.Net

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ASP.NET

Dear friends,
I have gridview and its contain textboxes and Im bind data to that textboxes now im want to make changes that text box data and transfer to DB,I'l do that inside the GridViewRowCommand event,but there are some issues,so im try that inside the GriViewRowUpdating event but that even is does not fire in edit button click event...Please help me????
//this my code

public void GridView1_RowUpdating(object sender, GridViewUpdateEventArgs e)
{

string CheckpointName = ((TextBox)GridView1.Rows[e.RowIndex]
.FindControl(somevalue)).Text;
string Query = "UPDATE check_points SET CHECKPOINT_NAME = '" + CheckpointName + "' WHERE ROOT_ID='" + TextBox1.Text + "'";
if (access.insert_delete_update(Query))
{
ScriptManager.RegisterStartupScript(this, this.GetType(),
"Message", "alert(Error);", true);
}
GridView1.EditIndex = -1;
GridView1.DataBind();

}