how to update table data in asp.net?

Here is the sql database table creating code:

CREATE TABLE tblCustomer
(
[id] [int] IDENTITY(1,1) NOT NULL,
[FirstName] [nvarchar](50) NULL,
[LastName] [nvarchar](50) NULL,
[Email] [nvarchar](200) NULL,
[Phone] [nvarchar](50) NULL
) 

A stored procedure to Update:

create proc sp_update_tblCustomer
(
@id int,
@name nvarchar(50),
@last nvarchar(50),
@email nvarchar(50),
@phone nvarchar(50)
)
as 
begin
update  tblCustomer  set
FirstName =@name,
LastName=@last,
Email=@email,
Phone  =@phone
where id = @id
end  

We need a Gridview to view data first:

   <asp:GridView runat="server" ID="GridView1" class="table table-bordered">
                   <Columns>
                       <asp:TemplateField  HeaderText="Edit">
                           <ItemTemplate>
                             <a href="inserCustomer.aspx?id=<%#Eval("id") %>"  >Edit</a>
                           </ItemTemplate>
                       </asp:TemplateField>
                   </Columns>
             </asp:GridView>

We also pass a parameter (id) by click edit button from Gridview then we need to load a single row data parameter wise for edit by above table.

  Here is all code behind:

 protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            showMain();
        }
    }

    private void showMain()
    {
        string id = Request.QueryString["id"];
        if (id!=null)
        {
            ShowDataIdWise();
        }
    }

    private void ShowDataIdWise()
    {
        string Edit_Id = Request.QueryString["id"];
        var dt = new DataTable();
        var da = new SqlDataAdapter("SELECT   * from tblCustomer where id=" + Edit_Id, con);
        con.Open();
        da.Fill(dt);
        con.Close();
        if (dt.Rows.Count > 0)
        {
            DataRow row = dt.Rows[0];
            txtName.Text = Convert.ToString(row["FirstName"]);
            txtLast.Text = Convert.ToString(row["LastName"]);
            txtEmail.Text = Convert.ToString(row["email"]);
            txtPhone.Text = Convert.ToString(row["phone"]);
        }
    }

    protected void btnUpdate_Click(object sender, EventArgs e)
    {
        string Edit_Id = Request.QueryString["id"];
        name = txtName.Text;
        last = txtLast.Text;
        email = txtEmail.Text;
        phone = txtPhone.Text;
        var cmd = new SqlCommand("sp_update_tblCustomer", con);
        cmd.CommandType = CommandType.StoredProcedure;
        cmd.Parameters.AddWithValue("@id", Edit_Id);
        cmd.Parameters.AddWithValue("@name", name);
        cmd.Parameters.AddWithValue("@last", last);
        cmd.Parameters.AddWithValue("@email", email);
        cmd.Parameters.AddWithValue("@phone", phone);
        con.Open();
        int m = cmd.ExecuteNonQuery();
        if (m != 0)
        {
            lblmsg.Text = "Data Updated Succesfully";
            lblmsg.ForeColor = Color.Green;
        }
        con.Close();
    }

Finally our output is here: