Throw Error as string in ASP.NET

Question

I have a class with this method:

public static DataTable getHeader(DALheader header)
{
    string sql = string.Format("EXECUTE getHeader @headerID = {0}", header.headerID);
    SqlDataAdapter headerAdapter = new SqlDataAdapter(sql, eformConnection);
    DataTable headerTable = new DataTable();

    try
    {
        headerAdapter.Fill(headerTable);
        return headerTable;
    }
    catch(Exception ex)
    {
        throw ex;
    }
}

on the code behind of an ASPX, I call this method. if i throw ex, you see the asp.net error in the browser. I want to keep them on the page and display the error. I put the method call in a try catch but that didn't do it, I can't return ex because I have to return a DataTable if I return anything. I'm not sure how to get the error message back to the page.

A few points: 1. Your SQL is vulnerable to injection. 2. There is no point catching then re-throwing an exception (in fact it clears the Stack trace, so never do this). 3. Your SQL connection object should not be static because static ASP.NET page fields are not thread safe at all. — Dai
– Dai, Commented Apr 19, 2013 at 0:37

Adrian Godong · Accepted Answer · 2013-04-19 02:10:12Z

2

Don't handle the exception on the database code but handle the exception on the page.

On the class:

public static DataTable getHeader(DALheader header)
{
    string sql = string.Format("EXECUTE getHeader @headerID = {0}", header.headerID);
    SqlDataAdapter headerAdapter = new SqlDataAdapter(sql, eformConnection);
    DataTable headerTable = new DataTable();
    headerAdapter.Fill(headerTable);
    return headerTable;
}

On the page:

try
{
    var headerTable = GetHeader();
}
catch(Exception ex)
{
     lblErrorMessage.Text = ex.Message;
}

answered Apr 19, 2013 at 2:10

Adrian Godong

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1 Comment

John Saunders Over a year ago

+1 but note that exception messages aren't always very pretty for users; and also that the OP may wish to log the complete exception somewhere (ex.ToString()) for troubleshooting purposes.

Iswanto San · Accepted Answer · 2013-04-19 00:40:10Z

0

You can catch the exception in your code behind and then print the error message.

Possible code:

try {
      // call getHeader method
}catch(Exception ex)
{
     // assume you have a label lblErrorMessage
     lblErrorMessage.Text = ex.Message;
}

answered Apr 19, 2013 at 0:40

Iswanto San

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1 Comment

Jon Baxter Over a year ago

see thats the thing. i dont do this on an aspx page, i do it in a class. otherwise i coulda done that. if i put a try catch around the call to the class, it doesnt matter, it throws the exception in the class

John Saunders · Accepted Answer · 2013-04-19 01:49:46Z

0

Simply do not catch exceptions that you cannot completely handle.

Your class cannot handle this exception because "handling" it consists of displaying it to the user. Your class knows nothing about the user.

Let a caller of your class catch the exception and display it to the user. Your class should have no try/catch block (and should also fix the other problems noted by @Dai).

answered Apr 19, 2013 at 1:49

John Saunders

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