CODEWITHSUNDEEP
c#.netexception.net-4.0
Ganesh Kumar
Ganesh Kumar

Reputation: 73

How to find which property of an object threw the exception C#

Is there a way to find out which property of the objects threw the exception. I have a Class with 3 properties. I want to give a message to the user that a particular property in the class is wrong. 

public class Numbers
{
    public string Num1 { get; set; }
    public string Num2 { get; set; }
    public string Num3 { get; set; }
}

class Program
{
    static void Main(string[] args)
    {
        var numbers = new Numbers() { Num1 = "22", Num2 = "err", Num3 = "33" };
        // Call an extension method which tries convert to Int
        var num = numbers.Num1.StringToInt();
         num = numbers.Num2.StringToInt();
         num = numbers.Num3.StringToInt();

        Console.WriteLine(num);
        Console.ReadLine();
    }
}

public static class SampleExtension
{
    static StackTrace stackTrace = new StackTrace(true);

    // Extension method that converts string to Int
    public static int StringToInt(this string number)
    {
        try
        {
            // Intentionally used 'Convert' instead of 'TryParse' to raise an exception
            return Convert.ToInt32(number);
        }
        catch (Exception ex)
        {
            // Show a msg to the user that Numbers.Num2 is wrong. "Input string not in correct format"
            var msg = stackTrace.GetFrame(1).GetMethod().ToString();
            msg = ex.Message;
            msg += ex.StackTrace;
            throw;
        }
    }
}

I'm using an extension method to convert sting to int. And i'm looking for a way to catch the wrong property in the extension method itself. I'm using .Net framework 4.0. Please suggest.

Upvotes: 0

Views: 687

Answers (4)

Reza ArabQaeni
Reza ArabQaeni

Reputation: 4908

public static int StringToInt(this Numbers number,
 Expression<Func<Numbers, string>> prop)
{
    try
    {
        return Convert.ToInt32(prop.Compile()(number));
    }
    catch (Exception ex)
    {
        var expression = (MemberExpression)prop.Body;
        string name = expression.Member.Name;
        throw new MissingMemberException(string.Format("Invalid member {0}", name));
    }
}

And call it:

var num = numbers.StringToInt(p=>p.Num1);

Upvotes: 0

Mat&#237;as Fidemraizer
Mat&#237;as Fidemraizer

Reputation: 64943

Note

I was answering this question based on .NET 4.5 because the question had no tag for an specific framework version. I leave the answer here because it may be useful for future visitors using .NET 4.5.

I would like to say that your code sample is very ugly since you could overcome this problem by using int.TryParse, but as I guess you wanted to show a generalized case (bad choice) and you just want to know the caller name of the extension method: check the [CallerMemeberNameAttribute] introduced in the 4.5 version of .NET Framework:

For example, either in an extension or regular method, do this:

public void Method([CallerMemberName] string callerName)
{
}

And the CLR will set the input parameter with the name of the caller!

Upvotes: 0

Sinatr
Sinatr

Reputation: 22008

Why not simply supply all needed data to the method during call? Schematically (you can extend it):

public static int ToInt(string number, string info)
{
    try
    {
        // ...
    }
    catch(Exception e)
    {
        MessageBox.Show(info);
    }
}

// and usage
string str1 = "123";
int n = ToInt(str1, "Trying to parsing str1");

Upvotes: 0

Davin Tryon
Davin Tryon

Reputation: 67336

I would use Int32.TryParse instead, then you can explicitly handle the failure to parse.

public static int StringToInt(this string number)
        {
            try
            {
                int result;
                if (!Int32.TryParse(number, out result))
                {
                    // handle the parse failure
                }
                return result;
            }
        }

Upvotes: 1

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