Compiler error in using block

Question

I am trying to catch any errors that crop up when a URL is invalid, below is the original code:

public static void mymethod()
{
    HttpWebRequest request = (HttpWebRequest)WebRequest.Create(firstline);
    Stopwatch timer = new Stopwatch();
    timer.Start();                
    using (var response = request.GetResponse())    
    timer.Stop();
    timeTaken = timer.Elapsed.ToString();
}

I have tried to create an exception handler as below, but no luck:

public static void mymethod()
{
    HttpWebRequest request = (HttpWebRequest)WebRequest.Create(firstline);
    Stopwatch timer = new Stopwatch();
    timer.Start();

    try
    {            
        using (var response = request.GetResponse())
    }    
    catch
    {
        Console.WriteLine("error here...")
    }

    timer.Stop();
    timeTaken = timer.Elapsed.ToString();
}

@avatishchev Error 4 Only assignment, call, increment, decrement, and new object expressions can be used as a statement — James
– James, Commented Aug 26, 2011 at 9:05
@James: please ask explicit questions. Yours turns out not to be about exception handling but about a simple syntax error. Always list the error message. — Henk Holterman
– Henk Holterman, Commented Aug 26, 2011 at 9:18

Jethro · Accepted Answer · 2011-08-26 09:07:09Z

2

You should do something like this.

public static void ShowResponseAndTimeTaken(string firstline)
{
    try
    {   
        HttpWebRequest request = (HttpWebRequest)WebRequest.Create(firstline);
        System.Diagnostics.Stopwatch timer = new Stopwatch();
        timer.Start();
        using (var response = request.GetResponse())
        {
            Console.WriteLine("Response : {0}", response);
        }
        timer.Stop();
        Console.WriteLine("Time taken : {0}", timer.Elapsed); 
    }
    catch(Exception e)
    {
        Console.WriteLine("error : {0}", e.Message);
    }      
}

answered Aug 26, 2011 at 9:07

Jethro

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Comments

abatishchev · Accepted Answer · 2011-08-26 09:06:50Z

1

Your usage of using-block is incorrect. The correct looks like this:

using (var response = request.GetResponse())
{
}

or just without the block:

var response = request.GetResponse();
response.Dispose()

answered Aug 26, 2011 at 9:06

abatishchev

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2 Comments

James Over a year ago

sorry I don't see what the purpose of this is, can you exaplain

abatishchev Over a year ago

@James: First of all, using block can't be used in one line, it should have underlying scope. Or just don't use it.

alexm · Accepted Answer · 2011-08-26 09:06:13Z

0

I believe you cannot intercept it because it is thrown before "try" block: it is possible that "firstline" variable contains a text with perhaps incorrectly formatted uri,

HttpWebRequest request = (HttpWebRequest)WebRequest.Create(firstline);

answered Aug 26, 2011 at 9:06

alexm

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Comments

TySu · Accepted Answer · 2011-08-26 09:09:35Z

0

You can also validate URL using regex instead of waiting for exception to be thrown - http://msdn.microsoft.com/en-us/library/system.text.regularexpressions.regex.aspx.

Here (http://msdn.microsoft.com/en-us/library/system.net.httpwebrequest.getresponse.aspx) you can find detailed description about GetResponse. Check what exceptions can be thrown and modify your current exception handling. You shouldn't leave try...catch as it is. At least catch Exception class.

answered Aug 26, 2011 at 9:09

TySu

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Comments

Paul Ruane · Accepted Answer · 2011-08-26 09:09:45Z

0

WebRequest.Create only throws if the scheme is invalid (the bit before the colon), there is a security error or if the URI you pass is null (although you have not enclosed that statement inside your try statement so such errors will be unhandled by the above code anyway).

To handle other errors, you should look at the HttpWebResponse.StatusCode property and handle the HTTP errors in way appropriate to your application.

answered Aug 26, 2011 at 9:09

Paul Ruane

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Comments

Jan · Accepted Answer · 2011-08-26 09:10:18Z

-1

I think you are talking about syntactic errors, because your code does not compile?

Try to add the missing semicolon on this line:

Console.WriteLine("error here...")

And the using-block contains no block:

using (var response = request.GetResponse())

remove the using:

var response = request.GetResponse())

answered Aug 26, 2011 at 9:10

Jan

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