C# If Contains?

Question

I am new to C# and I'm trying to write a contains statement. I want the process to read the test variable and if it contains the word error then print the variable if it does not contain an error then print no error. I think my process is close except when I run the code below I get an error when the CLI runs.

"object reference not set to an instance of an object"

Any help would be appreciated!

        while (true)
        {
            test = queue.GetMessage();
            if (test.AsString.Contains("error"))
            {
                Console.WriteLine(string.Format("Variable: {0}", test.AsString));

            }
            else
                Console.WriteLine(string.Format("No Error: {0}", test.AsString));
        }

you could tell us at least on which line the error occurs... — akonsu, Nov 20 '13 at 04:30
Something is `null` in your code. Either `test`, or whatever is returned from `AsString`. Why aren't you overriding `ToString` anyway? — Simon Whitehead, Nov 20 '13 at 04:31
Or if AsString is null. You can provide a ToString() override to the test object. — IAbstract, Nov 20 '13 at 04:32
Agree with nim. Either test is null, or queue was never fully define / created. — Inisheer, Nov 20 '13 at 04:32
What do you want the message to be when `queue.GetMessage()` is null? — Carbine, Nov 20 '13 at 09:16

score 2 · Answer 1 · edited May 23 '17 at 12:05

2

var message = queue.GetMessage()?? string.Empty;
var formattedMessage =
            String.Format(
                (message.IndexOf("error", StringComparison.OrdinalIgnoreCase) >= 0)
                    ? "No Error: {0}"
                    : "Variable: {0}", message);
Console.WriteLine(formattedMessage);

Useful references:

edited May 23 '17 at 12:05

Community

1
1

answered Nov 20 '13 at 09:41

Carbine

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String.Equals != Contains ? – Abhitalks Nov 20 '13 at 09:45
@abhitalks Sorry for the hasty edit.. Now I have corrected the mistake – Carbine Nov 22 '13 at 02:28

James Cronen · Accepted Answer · 2013-11-20T04:35:06.617

If queue.GetMessage() return a string, then you don't need AsString. If you want to convert it to a string, override ToString().

while (true) {
    test = queue.GetMessage();
    if (test.ToString().Contains("error")) {
        ...
    } else { 
        ...
    }
}

You can always guarantee that ToString() will be present because it's defined in the object base class. Just be sure it returns something intelligible, because default implementations may not.

C# If Contains?

2 Answers2