Debug ASP.NET pages using Tracing

In Classic ASP one might debug some code using VB Script:

Response.Write strSQL
Response.End()

and the comment/uncomment the code accordingly. This was a bit of a pain during the development process. In ASP.NET, one can use the Trace feature which simplifies matters somewhat. Page-level tracing can be set in the Page directive on the ASPX page:

<%@ Page Language="c#" Trace="true"%>

and in the code one could use:

string strSQL="select * from " + Table + " " + WhereClause + " order by " + OrderingColumn;
Trace.Write("SQL",strSQL);

When the page is run in the browser, you'll see:

So, you'd be able to see the SQL that is executed. By using Trace.Warn instead of Trace.Write, the line would be highlighted in Red. When the application is deployed, you'd simply disable tracing by setting the Trace attribute to false. If you have many pages that you wish to trace, then it may be more viable to set the tracing in your web.config file:

<system.web>
    <trace enabled="true" requestLimit="20" pageOutput="true" traceMode="SortByCategory" localOnly="true" />
</system.web>

So, you can easily enable/disable tracing as required.

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Julian Roberts I've been a freelance web developer since Feb '00. Prior to that, I'd spent most of my working life in the pub trade. I'd also worked as a security guard in a local factory. Luckily, I was able to ...

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