how to refresh gridview

protected void Button1_Click(object sender, EventArgs e)
{

string sqlCon = ConfigurationManager.ConnectionStrings["cnstr"].ToString();
SqlConnection con = new SqlConnection(sqlCon);
SqlCommand cmd = new SqlCommand();
if(Page.IsPostBack)
{
try
{
cmd.CommandType = CommandType.StoredProcedure;
cmd.CommandText = "VIEW_UPDATNGWBSTS";
cmd.Parameters.Add("@portno", SqlDbType.VarChar, 100).Value = TextBox2.Text.Trim();
cmd.Parameters.Add("@webname", SqlDbType.VarChar, 100).Value = TextBox1.Text.Trim();
//cmd.Parameters.Add("@CreatedDate", SqlDbType.Date);

cmd.Parameters.Add("@error", SqlDbType.VarChar, 100);
cmd.Parameters["@error"].Direction = ParameterDirection.Output;
cmd.Connection = con;
con.Open();
cmd.ExecuteNonQuery();
string msg;
msg = (string)cmd.Parameters["@error"].Value;
Label1.Text = msg.ToString();
}
catch (SqlException ex)
{
throw ex;
}
finally
{
cmd.Dispose();
if (con != null)
{
con.Close();
}}}}
STORED PROCEDURE
CREATE PROCEDURE VIEW_UPDATNGWBSTS
@webname varchar(100),
@portno varchar(100),
@error varchar(100) out
AS
BEGIN

declare @a int
declare @Createdate date
declare @a1 int
set @a=(select count(WebsiteName) from Websitedtls where WebsiteName=@webname)
set @a1=(select count(WebsiteName) from Updatngwbsts where WebsiteName=@webname)

if(@a=0)
begin
insert into Websitedtls (PortId,WebsiteName,Createdate)values(@portno,@webname,GETDATE())
set @error='updated successfully'
select WebsiteName from Websitedtls
if(@a1!=0)
delete from Updatngwbsts where WebsiteName=@webname
end
else
set @error='websitename already exist'

END
GO