Verify the type of custom class in function

Question

In C#,I have a public function that can pass a List parameter, with T is a custom class. The function can pass with different T class. The problem that how to verify the type of T in every case?

public static List<T> ConvertData(List<T> oldDatas)
{
  //I will analyze the object T, 
  //but now i don't know how to verify the type of T, 
  //with T  can change,
  //example maybe T is T1 class,or T2 class..
}

Thanks for my stupid question.

Which language ? `C#`, `Java`? Tag the question with correct programming language you are using. — Naveen, May 31 '11 at 09:41

score 2 · Answer 1 · edited May 23 '17 at 10:34

2

this is for C#

Type gt = typeof(T);

check this for java : Get generic type of java.util.List

edited May 23 '17 at 10:34

Community

1
1

answered May 31 '11 at 09:43

Pranay Rana

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score 2 · Answer 2 · edited May 31 '11 at 10:55

2

Do you need to make different converting depends on or just want to check for specific classes? In second case you can try to specify right types for T something like:

public static List<string> ConvertData(List<string> data)
{
    return PrivateConvertData<string>(data);
}

public static List<int> ConvertData(List<int> data)
{
    return PrivateConvertData<int>(data);
}

private static List<T> PrivateConvertData<T>(List<T> data)
{
    // code here
}

This code will check type of T during compilation.

edited May 31 '11 at 10:55

abatishchev

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answered May 31 '11 at 10:11

chopikadze

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Because T is a sql to Linq class, so that it have some properties in every T object. How can I get propeties? – phamminh05 Jun 01 '11 at 03:18
Do you need the same properties from different classes or your properties list depends on your class? – chopikadze Jun 01 '11 at 09:19

score 2 · Answer 3 · answered May 31 '11 at 10:54

just do :

public static class Test<T> 
    where T : class, new()
{
    public static List<T> ConvertData(List<T> oldDatas)
    {
        T instanceOfT = new T();
        Type typeOfT = typeof(T); // or instanceOfT.GetType();

        if(instanceOfT is string)
        {
            // T is a string
        }
        else if(instanceOfT is int)
        {
            // T is an int
        }
        // ...
    }
}

But that isn't productive and break the generic concept... Explain what you're trying to do.

score 1 · Answer 4 · edited May 23 '17 at 12:10

You can use the typeof(T) keyword or use some check (if you are expecting some types to be passed via parameters):

 public static List<T> ConvertData(List<T> oldDatas)
 {
     foreach (var itemList in oldDatas)
     {
         if (itemList is LinqType)
         {
             var linqTypeItem = (LinqType) itemList;
             Console.WriteLine(linqTypeItem.PROPERTY_YOU_NEED);
         }
         // or
         var linqTypeItem = itemList as LinqType;
         if (linqTypeItem != null)
         {
             Console.WriteLine(linqTypeItem.PROPERTY_YOU_NEED);
         }
     }
 }

Also you can use the Cast() method. More information here

In here, T is a object of Linq. So that how can I get the property of object. — phamminh05, Jun 01 '11 at 00:22

Verify the type of custom class in function

4 Answers4