Edit Sql Database Using Gridview Asp.net c#

i'm trying to edit the information of Student table using gridview in c# but my code updates the gridview without changing the table in my sql database I don't know where is the problem
Here is my gridview :

<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" 
              DataKeyNames="S_ID"  OnRowCancelingEdit="GridView1_RowCancelingEdit"
            OnRowEditing="GridView1_RowEditing" OnRowUpdating="GridView1_RowUpdating" AllowPaging="true" >
              <Columns>

              <asp:TemplateField HeaderText="ID">
                    <EditItemTemplate>
                        <asp:TextBox ID="S_ID" runat="server" Text='<%# Eval("S_ID") %>'></asp:TextBox>
                    </EditItemTemplate>
                    <ItemTemplate>
                        <asp:Label ID="Label1" runat="server" Text='<%# Bind("S_ID") %>'></asp:Label>
                    </ItemTemplate>
                </asp:TemplateField>

                <asp:TemplateField HeaderText="Name">
                    <EditItemTemplate>
                        <asp:TextBox ID="S_Name" runat="server" Text='<%# Eval("S_Name") %>'></asp:TextBox>
                    </EditItemTemplate>
                    <ItemTemplate>
                        <asp:Label ID="Label1" runat="server" Text='<%# Bind("S_Name") %>'></asp:Label>
                    </ItemTemplate>
                </asp:TemplateField>

                <asp:TemplateField HeaderText="Email">
                    <EditItemTemplate>
                        <asp:TextBox ID="S_Email" runat="server" Text='<%# Eval("S_Email") %>'></asp:TextBox>
                    </EditItemTemplate>
                    <ItemTemplate>
                        <asp:Label ID="S_Email" runat="server" Text='<%# Bind("S_Email") %>'></asp:Label>
                    </ItemTemplate>
                </asp:TemplateField>

                  <asp:CommandField ShowEditButton="True" />
              </Columns>
          </asp:GridView>

and this is the code behind:

protected void gvbind()
    {
        SqlConnection conn = new SqlConnection(@"MYCONNECTION");
        conn.Open();
        SqlCommand cmd = new SqlCommand("SELECT S_ID , S_Name , S_Email , B_ID FROM Student", conn);

        DataTable dt = new DataTable();
        dt.Load(cmd.ExecuteReader());
        GridView1.DataSource = dt; // now assign this datatable dt to gridview as datasource
        GridView1.DataBind();
    }
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!this.IsPostBack)
        {
            gvbind();
        }
    }

    protected void GridView1_RowEditing(object sender, GridViewEditEventArgs e)
    {
        GridView1.EditIndex = e.NewEditIndex;
        gvbind();
    }

    protected void GridView1_RowUpdating(object sender, GridViewUpdateEventArgs e)
    {


        int sUserId = Convert.ToInt32(GridView1.DataKeys[e.RowIndex].Value.ToString());
        TextBox name = (TextBox)GridView1.Rows[e.RowIndex].FindControl("S_Name"); //give the edititem template ID
        TextBox email = (TextBox)GridView1.Rows[e.RowIndex].FindControl("S_Email");
        try
        {
            SqlConnection conn = new SqlConnection(@"MYCONNECTION");
            conn.Open();
            SqlCommand c = new SqlCommand("Update Student set S_Name='" + name.Text + "',S_Email='" + email.Text + "'where S_ID='" + sUserId + "'");
            c.Connection = conn;
            c.ExecuteNonQuery();

            GridView1.EditIndex = -1;
            gvbind();
        }
        catch (Exception ex)
        {
            Page.ClientScript.RegisterStartupScript(typeof(string), "Key", "alert('Error : \\n" + ex.Message + "');", true);
        }
    }

    protected void GridView1_RowCancelingEdit(object sender, GridViewCancelEditEventArgs e)
    {
        GridView1.EditIndex = -1;
        gvbind();
    }

please can anyone help me why this change the gridview only but not the DB ?!