SqlDataReader.GetString Error: Invalid Arguments

Question

When I run my problem, it shows this error:

The best overloaded method match for 'System.Data.Common.DbDataReader.GetString(int)' has some invalid arguments.

My code:

SqlConnection con = new SqlConnection(ConnectionClass.connectionclass);
    SqlCommand com;
    SqlDataReader dr;
private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
    {
        con.Open();
string query = "SELECT * FROM student WHERE Name = '"+comboBox1.Text+"'";
        com = new SqlCommand(query, con);
        dr = com.ExecuteReader();
        while (dr.Read())
        {
            string abc = dr.GetString("Name");

        }

    }

ok...i have searched for the answer and tried but the problem persists. — Ali Raza, Mar 01 '15 at 18:09
@Patrick Hofman: http://stackoverflow.com/questions/3639861/why-is-select-considered-harmful — user2672165, Mar 01 '15 at 18:38
i removed other columns, it was just to describe my problem. — Ali Raza, Mar 01 '15 at 18:38
[SQL Injection alert](http://msdn.microsoft.com/en-us/library/ms161953%28v=sql.105%29.aspx) - you should **not** concatenate together your SQL statements - use **parametrized queries** instead to avoid SQL injection — marc_s, Mar 01 '15 at 19:18

score 3 · Accepted Answer · answered Mar 01 '15 at 18:14

3

You should supply the column ordinal number, not the column name to the SqlDataReader.GetString method:

var ordinal = dr.GetOrdinal("Name");
while (dr.Read())
{
    string abc = dr.GetString(ordinal);

}

answered Mar 01 '15 at 18:14

Martin Liversage

100,656
22
201
249

i did it by this `dr.GetString(dr.GetOrdinal("Name"));` – Ali Raza Mar 01 '15 at 18:37
1

@Ali: that can have a serious performance impact. Listen to Martin (he has some reputation on this site so he knows...). – Patrick Hofman Mar 01 '15 at 18:57

SqlDataReader.GetString Error: Invalid Arguments

1 Answers1