Edit, delete and update in gridview

hi , i have a gridview and i have edit, delete and update buttons.i can use edit and delete buttons they work but update button doesn't work when i click on update button ,the page refreshes ,doesn't update.please help me.here is my code...
runat="server"
AutoGenerateColumns="false"
OnRowUpdating="GV_RowUpdating"
OnRowDeleting="GV_RowDeleting"
OnRowEditing="GV_RowEditing"
OnRowCancelingEdit="GV_RowCancelingEdit">































CommandName="Update" Text="Update">
  CommandName="Cancel" Text="Cancel">


CommandName="Edit" Text="Edit">
  CommandName="Delete" Text="Delete">





code behind...

protected void Page_Load(object sender, EventArgs e)
{
Bind();
}
public void Bind()
{
try
{
CTeam cTeam = new CTeam();
GridviewTeams.DataSource = cTeam.GetAllTeams();
GridviewTeams.DataBind();
}
catch (Exception err)
{
Response.Write(err.Message);
}
}
protected void BtnAdd_Click(object sender, EventArgs e)
{
CTeam cteam = new CTeam();
cteam.AddTeams(tbxTeamName.Text,tbxTeamEmail.Text);
Bind();
}
protected void GV_RowDeleting(object sender, GridViewDeleteEventArgs e)
{
CTeam cteam = new CTeam();
int indexrow = e.RowIndex;
short tid = short.Parse(((Label)GridviewTeams.Rows[indexrow].FindControl("GV_lblTeamID")).Text);
cteam.DeleteTeams(tid);
Bind();
}
protected void GV_RowEditing(object sender, GridViewEditEventArgs e)
{
GridviewTeams.EditIndex = e.NewEditIndex;
Bind();
}
protected void GV_RowCancelingEdit(object sender, GridViewCancelEditEventArgs e)
{
GridviewTeams.EditIndex = -1;
Bind();
}
protected void GV_RowUpdating(object sender, GridViewUpdateEventArgs e)
{
CTeam cteam = new CTeam();
int indexrow = e.RowIndex;
string tname = ((TextBox)GridviewTeams.Rows[e.RowIndex].FindControl("tbxEditTeamName")).Text;
string temail = ((TextBox)GridviewTeams.Rows[e.RowIndex].FindControl("tbxEditTeamEmail")).Text;
cteam.UpdateTeams(tname, temail);

GridviewTeams.EditIndex = -1;
Bind();
}
}