C＃sql like语句不起作用

Question

Hello and good day to all. I have a little question about like statement of sql/c#, I can't figure out why my code doesn't work.

if (Combo_List.Text == "What")
{
   listView1.Items.Clear();
   myds.Clear();
   mydaEvents.SelectCommand = myconn.CreateCommand();
   mydaEvents.SelectCommand.CommandText = "select * from Eventstbl where What like '@what%'";
   mydaEvents.SelectCommand.CommandType = CommandType.Text;
   mydaEvents.SelectCommand.Parameters.Add("@what", SqlDbType.NVarChar, 2000, "What").Value = text_Search.Text;
   mydaEvents.Fill(myds, "Eventstbl");

   foreach (DataRow item in myds.Tables["Eventstbl"].Rows)
   {
       ListViewItem items = new ListViewItem(item["EventsID"].ToString());
       items.SubItems.Add(item["What"].ToString());
       listView1.Items.Add(items);
   }
}

The @what% won't work but when I put 'a%' all items that begin in letter a shows in my listview1. I don't know how to fix this issue. help me please. Thank you in advance.

Answer 1

Try this:

mydaEvents.SelectCommand.CommandText = "select * from Eventstbl where What like @what + '%'";

Text inside quotes will be treated as...text - you want your parameter to be interpreted as its string value , so you have to move it out.

Answer 2

I'm guessing the problem is that '@what%' is being treated as a literal rather than getting replaced with the value of your parameter.

Try doing @what + '%' instead.