ODBC must declare the scalar variable

问题

Consider the code below:

string ConnectionString = "dsn=mysql;uid=sa;DATABASE=userdb;";
string qryStr = "insert into info(code) values(@code);";
OdbcConnection con = new OdbcConnection(ConnectionString);
OdbcCommand cmd = new OdbcCommand(qryStr,con );
cmd.Parameters.Add("@code", System.Data.Odbc.OdbcType.Int).Value = "999";
cmd.Connection.Open();
OdbcDataReader odbcdtr = cmd.ExecuteReader();//exception "must declare the scalar  variable @code"
con.Close;

This code is raising exception "must declare scalar vairable @code". I'll be very grateful if anyone can point out the mistake that is in the code above.

回答1:

I've finally found the solution as given in this link.

The Odbc interface does not recognise the use of @named variables, only ? which are taken by position. You can use ?Param1, ?Param 2 for readability, but the position is all that is used.

回答2:

Try

string ConnectionString = "dsn=mysql;uid=sa;DATABASE=userdb;";
string qryStr = "insert into info(code) values(?code);";
OdbcConnection con = new OdbcConnection(ConnectionString);
OdbcCommand cmd = new OdbcCommand(qryStr,con );
cmd.Parameters.Add("@code", System.Data.Odbc.OdbcType.Int).Value = 999;
cmd.Connection.Open();
OdbcDataReader odbcdtr = cmd.ExecuteReader();
con.Close;

回答3:

Worked 100% please try this

byte[] imageDatas = ReadFile(strFn);
try
{
    if (con.State == ConnectionState.Open)
    {
        con.Close();
    }
    con.Open();
    OdbcCommand cmd = new OdbcCommand("insert into students(id,name,img) values(" + txtId.Text + ",'" + txtName.Text + "',?)", con);

    cmd.Parameters.AddWithValue("@img", imageDatas);

    cmd.ExecuteNonQuery();
    MessageBox.Show("inserted successfully");
    con.Close();

}
catch (Exception ex)
{
    MessageBox.Show(ex.Message);

}

来源：https://stackoverflow.com/questions/16480827/odbc-must-declare-the-scalar-variable