About the use of parameters ~ oledb

halala

Does that older brother have time?
A little question about the use of parameters
I look at msdn and can't understand
  string sql = "select * from members where userName =?";

What does this question mark mean?

What then? How to use Parameters?
I originally wrote this, but it is said that a question mark must be used
string sql = "select * from members where userName = @ name";
What should I write with a question mark?

maodanyun

Who told you the question mark must be used? Wasn't your original good?
SqlConnection MyConn = new .........
string sql = "select * from members where userName = @ name";
SqlCommand MyComm = new SqlCommand (sql, MyConn);

MyComm.Parameters.Add ("@ name", SqlDbType.VarChar, 20);
.........

halala

Can you help me to see what is wrong in the following paragraph? Report an error at ds.fill
OleDbConnection con = new OleDbConnection ("server = lo; uid = sa; pwd = sa; database = test; Provider = SQLOLEDB");
   string sql = "select * from members where userName = @ userName";
    con.Open ();
    OleDbDataAdapter da = new OleDbDataAdapter (sql, con);
 da.SelectCommand.Parameters.Add ("@ userName", this.TextBox1.Text.Trim ());
  DataSet ds = new DataSet ();
   da.Fill (ds);
  con.Close ();
  this.DataGrid2.DataSource = ds.Tables [0];
  this.DataGrid2.DataBind ();

psycholmu

What is wrong?

halala

Must declare parameters
But haven't I already declared it?

halala

It is said that oledb must use "?" (Question mark), not directly @name
How to write with question mark?
Thank you for your advice, thank you ~

halala

I figured it out myself
Hee hee