get an error as ExecuteNonQuery:Connection property has not been initialized

Question

string connectionString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:\\Samples\\login.mdb";
String uname, pass;
uname = textBox1.Text;

pass = textBox2.Text; 
OleDbConnection myConnection = new OleDbConnection(connectionString);
myConnection.Open();

String query = "insert into LOGIN_TABLE (UserName, Password) VALUES ('" +
    textBox1.Text.ToString() + "','" + textBox2.Text.ToString() + "') ";


OleDbCommand myCommand = new OleDbCommand();
myCommand.CommandText = query;
OleDbParameter myParm = myCommand.Parameters.Add("@uname", OleDbType.VarChar, 50);
myParm.Value = textBox1.Text;

myParm = myCommand.Parameters.Add("@pass", OleDbType.VarChar, 50);
myParm.Value = textBox2.Text;

myCommand.ExecuteNonQuery();
myConnection.Close();

Answer 1

You haven't told your OleDbCommand which database connection to use.

Try doing this instead:

OleDbCommand myCommand = new OleDbCommand(query, myConnection);

And then don't set the CommandText property on the next line.

Update: Marc was right, you weren't even using your parameters because your query definition didn't lend itself to what's called a Prepared Statement. Try this:

string connectionString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:\\Samples\\login.mdb";

using (OleDbConnection myConnection = new OleDbConnection(connectionString))
{
    myConnection.Open();

    string query = "INSERT INTO LOGIN_TABLE (UserName, Password) VALUES (?, ?)";

    OleDbCommand myCommand = new OleDbCommand(query, myConnection);

    myCommand.Parameters.Add("UserName", OleDbType.VarChar, 50);
    myCommand.Parameters.Add("Password", OleDbType.VarChar, 50);

    myCommand.Parameters[0].Value = textBox1.Text;
    myCommand.Parameters[1].Value = textBox2.Text;

    myCommand.Prepare();
    myCommand.ExecuteNonQuery();
}

I got rid of some unnecessary assignments and set up your command parameters a little differently. Give it a shot and let me know if that solves your problem.