Question

I have a requirement where I can get the following in an object –

a type T or List<T>  

Converting object into T is easy. How can I convert it to List(by first checking that it can be converted successfully or not), reason I want to convert is to scroll through the list and call tostring on each element.

My actual code –

namespace Generic_Collection_Code {     class Program     {         public static string DumpObj(object obj)         {             string sTemp = String.Empty;              List<int> ints = obj as List<int>;             if (ints != null)             {                 foreach (int i in ints)                     sTemp += i.ToString() + ',';                 sTemp.Trim(',');             }             else              {                 List<string> strings = obj as List<string>;                 if (strings != null)                 {                     foreach (string s in strings)                         sTemp += s + ',';                     sTemp.Trim(',');                 }                 else                 {                     sTemp += obj.ToString();                 }             }             return sTemp;         }         static void Main(string[] args)         {             List<int> listInts = new List<int>();             listInts.Add(1);             listInts.Add(2);             listInts.Add(3);              Console.WriteLine('Object1: {0}', DumpObj(listInts));             int i = 90;              Console.WriteLine('Object2 {0}', DumpObj(i));               List<string> listStrings = new List<string>();             listStrings.Add('1');             listStrings.Add('2');             listStrings.Add('3');              Console.WriteLine('Object3: {0}', DumpObj(listStrings));             Console.ReadKey();         }     } } 

The above code works but I know its an ugly way to achieve this. I wanted to ask from community how can I have this function like –

    public static string DumpObj<T>(object obj)     {         string sTemp = String.Empty;          List<T> list = obj as List<T>;         if (list != null)         {             foreach (T i in list)                 sTemp += i.ToString() + ',';             sTemp.Trim(',');         }         return sTemp;     } 

This gives me compilation errors as I have to specify T while calling DumpObj with error as –

Error 1 The type arguments for method ‘Generic_Collection_Code.Program.DumpObj(object)’ cannot be inferred from the usage. Try specifying the type arguments explicitly. D:\DotNet\Generic_Collection_Code\Generic_Collection_Code\Program.cs 57 47 Generic_Collection_Code

as you can see, obj is an object, i dont know its type while calling dumobj.

I hope I have made myself clear on this one.

I appreciate your time!

Regards Amit

Answer 1

What is the compilation error you’re getting? If T is declared as a generic type parameter in your context then then the only compile-time issue I can see with that statement is the use of the keyword object as a variable name. At any rate, I’d suggest something like this as best expressing your intention:

IEnumerable enumerable = obj as IEnumerable;  if (enumerable != null) {     foreach (object item in enumerable)     {         sTemp += item.ToString();     } } 

You may also want to consider using a StringBuilder if your list is likely to have a lot of items.