Question

I have a function that returns a list of email addresses from a SQL stored Proc based on an ID called. It is using StringBuilder and returns one column. For most IDs there are 4 or less email addresses and this format is fine. However we are now getting more IDs with 10+ email addresses and this is making the page too long.

The function is:

DataTable dt = DAL.ExecStoredProc(DAL.DatabaseName.DB, "storedProc", param);
StringBuilder sb = new StringBuilder();
sb.Append("<br/><br/>");
sb.Append("<table border='0' cellpadding='3'>");
for (int i = 0; i < dt.Rows.Count; i++)
{
    sb.Append("<tr><td>");
    sb.Append(dt.Rows[i]["EMail"].ToString());
    sb.Append("</td></tr>");
}
sb.Append("</table>");
return sb.ToString();

I have tried using the following but it breaks when there are too few addresses to return:

DataTable dt = DAL.ExecStoredProc(DAL.DatabaseName.DB, "storedProc", param);
StringBuilder sb = new StringBuilder();
sb.Append("<br/><br/>");
sb.Append("<table border='0' cellpadding='3'>");
for (int i = 0; i < dt.Rows.Count; i++)
{
    sb.Append("<tr><td>");
    sb.Append(dt.Rows[i]["EMail"].ToString());
    i++;
    sb.Append("</td>");
    sb.Append("<td>");
    sb.Append(dt.Rows[i]["EMail"].ToString());
    i++;
    sb.Append("</td>");
    sb.Append("<td>");
    sb.Append(dt.Rows[i]["EMail"].ToString());
    i++;
    sb.Append("</td></tr>");
}
sb.Append("</table>");
return sb.ToString();

Answer 1

Using Linq’s Take function, you could replace the following block of code from your first example:

for (int i = 0; i < dt.Rows.Count; i++)
{
    sb.Append("<tr><td>");
    sb.Append(dt.Rows[i]["EMail"].ToString());
    sb.Append("</td></tr>");
}

with this:

foreach (var row in dt.Rows.OfType<DataRow>().Take(3))
{
    sb.Append("<tr><td>");
    sb.Append(row["EMail"].ToString());
    sb.Append("</td></tr>");
}

Since Take returns up to the specified number of elements from the beginning of the sequence, this block of code will be run anywhere from 0 to 3 times. You’ll have 3 addresses displayed at most (even if more are present), and you won’t get an IndexOutOfRangeException if you have less than 3.

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UPDATE: ASP.NET 2.0 Compatible

Since you can’t use Linq, this should have the same result:

for (int i = 0; i < (dt.Rows.Count > 3 ? 3 : dt.Rows.Count); i++)
{
    sb.Append("<tr><td>");
    sb.Append(dt.Rows[i]["EMail"].ToString());
    sb.Append("</td></tr>");
}

The expression dt.Rows.Count > 3 ? 3 : dt.Rows.Count uses the ? operator to cause the for loop to iterate over all of the email addresses unless there are more than 3, in which case it will iterate only 3 times.