How To Update Rows Data in Database ms Access With Parameter in C#

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C#

i use Database ms Access, and i try to Update some Rows with use parameters like code below

 OleDbCommand cmdEditOffline = new OleDbCommand();
 cmdEditOffline.CommandText = "UPDATE  TbTransactionToOffline SET Amount = @Amount  WHERE NoRef = @NoRef";
cmdEditOffline.Connection = conn;
cmdEditOffline.Parameters.Add("@Amount", OleDbType.VarChar).Value = txtAmount.Text;
cmdEditOffline.Parameters.Add("@NoRef", OleDbType.VarChar).Value = label1.Text;
if (conn.State == ConnectionState.Closed) conn.Open();
cmdEditOffline.ExecuteNonQuery();
this.Close();

i hope is that the data is updated in accordance with the parameters, but instead all data is updated.
what wrong?