What does, Must declare the scalar variable @vendor mean?

Question

I have read other posts and tried, changed and tried again only to be back to the code below. I can't figure out why "@vendor" is not declared. It must be something very simple and I have looked for so long that I just can't see it.

private string Get_Vendor_ID()
{
    string vendor_ID = "";
    string vendor = vendorTextBox.Text;
    string SQL = "SELECT Vendor_ID FROM Vendor WHERE Vendor_Name = @vendor";
    SqlCommand sqlCommand = new SqlCommand(SQL, DataAccessClass.sql_Connection);
    sqlCommand.Parameters.AddWithValue("@vendor_ID", vendor_ID);
    sqlCommand.Parameters.AddWithValue("@Vendor_Name", vendor);
    DataAccessClass.OpenConnection();
    SqlDataReader sqlDataReader = sqlCommand.ExecuteReader();

    while (sqlDataReader.Read())
    {
        vendor_ID = sqlDataReader["Vendor_ID"].ToString();
    }
    DataAccessClass.CloseConnection();
    return vendor_ID;
}

Any advise would be great.

Answer 1

Look at this specific line,

sqlCommand.Parameters.AddWithValue("@vendor_ID", vendor_ID);
sqlCommand.Parameters.AddWithValue("@Vendor_Name", vendor);

There is no @vendor declaration

try changing it to.

string SQL = "SELECT Vendor_ID FROM Vendor WHERE Vendor_Name = @Vendor_Name";