Check if argument of type object casts to integer or string

Question

I have a method that I want to serve as dual purpose, depending on whether the argument being passed is actually an integer or string value.

How would i check if 'info' in the following is an integer or string value?

public void Place (object info){


}

I know about overloading, but for reasons I won't go into can't change the calling method. Type 'object' is always being passed. Kind of kludgy but going to test for integer and string cast values.

Integer.TryParse: msdn.microsoft.com/en-us/library/f02979c7(v=vs.110).aspx . Although, pedantically, a false result just proves it's not an int32, not that it is unparseable as any other kind of number. Anything can be a string. Do you mean it must be only interpretable as a string, or merely not interpretable as an int? P.S. Overloading as suggested by Plutonix is arguably a cleaner and clearer approach. — ADyson
– ADyson, Commented Dec 30, 2017 at 20:59

Ousmane D. · Accepted Answer · 2017-12-30 21:08:53Z

4

Don't use object as the parameter, a better option would be to overload the method.

public void Place (string info){ ... }

public void Place (int info){ ... }

if you can't change the method signature for some reason then you'll need to do:

public void Place(object info)
{
       if(info is int){
           int result = (int)info;
           ...                   
       }
       else if (info is string){
           string result = (string)info;
           ...
       }
}

edited Dec 30, 2017 at 21:08

answered Dec 30, 2017 at 21:01

Ousmane D.

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2 Comments

Bachalo Over a year ago

yes, I know about overloading, but for reasons I won't go into can't change the calling method. Type 'object' is always being passed. Kind of kludgy but going to test for integer and string cast values.

Alexei Levenkov Over a year ago

@eco_bach you should have put that into question from the beginning. I did that for you... please try to put all information you have into questions in the future.

Sievajet · Accepted Answer · 2018-01-01 02:31:34Z

C# 7.0 introduced pattern matching. This enables matches based on a specific class or structure. Since you can't change the signature of the method, this is the best option at the moment.

Code becomes simpler using the is expression to assign a variable if the test succeeds:

public void Place( object info )
{
    if ( info is string infoString )
    {
        // use infoString here
    }
    else if ( info is int infoInt )
    {
        // use infoInt here                
    }
}

If statements are limited to test the input to match a specific single type. If you want to test specific cases, the switch pattern matching becomes a better choice:

public void Place( object info )
{
    switch ( info )
    {
        // handle a specific case
        case string infoString when infoString.Contains( "someInfo" ):
            // do something
            break;

        case string infoString:
            // do something
            break;

        case int infoInt when infoInt > 10:
            // do something
            break;

        case int infoInt:
            // do something
            break;

        default: 
        // handle any other case
        break; 
    }
}

Rahul · Accepted Answer · 2017-12-30 21:03:27Z

1

Or, make it a generic method like

public void Place<T> (T info)
{   
   // your code here
}

You can call it closing the type like

Place<int>(23) Or just Place(23)

answered Dec 30, 2017 at 21:03

Rahul

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2 Comments

Alexei Levenkov Over a year ago

Turned out OP can't change signature... Also I don't think it helps much in providing different versions of the code for Place method depending on type but rather just making type easier to obtain - still need if of some sort to check type.

Rahul Over a year ago

@AlexeiLevenkov. that's strange ... signature can't be changed but the code can be. Well in that case as well you can use this as wrapper

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