It all depends upon which method you are using. If you are using a
datareader, you can't do this because a datareader provides a row by row
look a the records. It doesn't jump around, just moves to the next row. A
datareader also doesn't know how many records are being returned so it's not
possible to look for a single one.

What you want is a datatable probably. A datatable is an xml structure
created by ado.net to hold the results of your query. It has rows and column
and you can visualize it as a spreadsheet. You can use the Rows.Count
property to find the number of rows, just in case there is no row 45 for
your customers (and remember, 0 is the first row and 1 is the second, all
arrays begin with zero).

DataTable myTable = ... populate table from query
string customer = string.Empty;
if(myTable.Rows.Count >= 45)
{
    // the following gets the value in column 0 of row number 45
   customer = myTable.Rows[44][0].ToString();
}