I'm coding something pretty common - using form input to create a dynamic database query and displaying the results. However, some of the form controls are multi-select boxes, so my query winds up containing a lot of loops and looking pretty messy.

 Any suggestions/example code on the best approach? Any links to a good tutorial on this? C# preferred but other languages OK.

not sure if this may be considered best practice but here's what I do

you can use good old Request.Form [ formControlID ]  to get a comma-separated list of selected values in a multi-select control, such as a ListBox.

this sample may not be exactly what you need, but at least you can get the idea

Here is what my query looks like so far, based on input from the first multi-select listbox. Is there a way to do this without all the looping?

// Declare the query string.
String queryString = "SELECT my_ID, my_Name FROM my_tbl";
// if mylist contains at least one item
if (PreviousPage.myList.Count > 0)
{
    // loop through array and add to query
    foreach (int myIDInt in myArray)
        {
            int i = 0;
            i++;

            if (i == 1)
                {
                    queryString += " AND (my_ID = @myIDInt";
                }
                else
                {
                    queryString += " OR my_ID = @myIDInt";
                }

                if ((myArray.GetLength(0) + 1) == i)
                {
                    queryString += ")";
                }
        }
}

Did you try our EasyQuery library: http://devtools.korzh.com/eq/dotnet/

It is free for non-commercial use.