C# Error: Index was outside the bounds of the array

Question

i am getting an "Index was outside the bounds of the array." at dr1[1].ToString().

I have table contribution_master with 3 columns: type_id (int), name (varchar(20), amount (float). I want to extract all the amount rows.

SqlConnection SQLCon1 = new SqlConnection(ConfigurationManager.ConnectionStrings["PayrollConnStr"].ConnectionString.ToString());

    SqlCommand SQLCmd1 = new SqlCommand("SELECT amount FROM contribution_master", SQLCon1);

    try
    {
        SQLCon1.Open();
        SqlDataReader dr1 = SQLCmd1.ExecuteReader();
        while (dr1.Read())
        {
            employer_epf = Convert.ToDouble(dr1[0].ToString());
            employer_admin = Convert.ToDouble(dr1[1].ToString());
            employer_edli = Convert.ToDouble(dr1[2].ToString());
            employer_admin_edli = Convert.ToDouble(dr1[3].ToString());
            employer_esi = Convert.ToDouble(dr1[4].ToString());
        }
    }
    catch (SqlException ex)
    {
        string errorMessage = "Error ";
        errorMessage += ex.Message;
        lblWarn.Text = errorMessage;
        lblWarn.Visible = true;
    }
    finally
    {
        SQLCon1.Close();
    }

Solution 1

The dr1[x] value relates to the position of the column it has read from the database.

The SQL you specify SELECT amount FROM contribution_master will return the amount column, however the data in this can only be accessed either using dr1[0] or dr1["amount"].

while (dr1.Read()) will iterate through each row of data in a loop until there is no more. However, if you need to access each row specifically, you might be better off filling the data into a datatable and assigning the values from there.

For example:

SqlDataAdapter da = new SqlDataAdapter(SQLCmd1);
DataTable dt = new DataTable();
da.Fill(dt);

employer_epf = Convert.ToDouble(dt.Rows[0][0].ToString());
employer_admin = Convert.ToDouble(dt.Rows[1][0].ToString());
employer_edli = Convert.ToDouble(dt.Rows[2][0].ToString());
employer_admin_edli = Convert.ToDouble(dt.Rows[3][0].ToString());
employer_esi = Convert.ToDouble(dt.Rows[4][0].ToString());

Hopefully this helps, but would it not be easier to have the axis of your table the other way around?

Solution 2

You're only returning one field from your query (amount) so there is only one field in the datareader (field 0)

Each call to datareader.Read() returns a single row. If you want subsequent rows, call Read() again.

So, in your code...

if (dr1.Read())
{
    employer_epf = Convert.ToDouble(dr1[0].ToString()); 
    if (dr1.Read())
    {
        employer_admin = Convert.ToDouble(dr1[0].ToString()); 
        // etc...
    }
}

Or you can populate a DataTable that will return all the rows at once.