C# enum query linq and general type?

Question

So I want to know that, from my enum value list, how many specific enum value exists.

So I wrote like

public int GetNumFromList(List<Elements> list, Elements eType)
{        
    IEnumerable<Elements> query = //list.Where(p => p.GetType() == eType);
        from listchild in list
        where listchild == eType
        select listchild;
    /*
    Debug.Log("Cur check type is " + eType + " and now selected number is " + query.Count());
    if(query.Count() > 0)
        Debug.Log(" and query 0 value is "+ query.ToArray().GetValue(0) + " type is "+ query.ToArray().GetValue(0).GetType());
        */
    return query.Count();
}
  public enum Elements{Fire, Water, Wood, Metal, Earth, None}

So this works well, but can I make this more shorter and neat?

//list.Where(p => p.GetType() == eType);  This part doesn't worked.

And how can make this for generic type, T?

Answer 1

This should work for enums and value types

public int GetNumFromList<T>(List<T> list, T item)
{
    return list.Count(x => x.Equals(item));           
}

Answer 2

尝试这个：

IEnumerable<Elements> query = list.Where(p => p == eType);

Answer 3

You can do it as short as this:

public int GetNumFromList(List<Elements> list, Elements eType)
{
  return list.Count(x => x == eType);
}

The generic version:

public int GetNumFromList<T>(List<T> list, T eType)
{
  return list.Count(x => x.Equals(eType));
}

Notice your classes should override Equals method in the generic case.

Answer 4

how can I make it for T general type? not only for [Elements] enum.

public int GetNumFromList<T>(IEnumerable<T> list, T eType)
     where T : struct, IComparable, IFormattable, IConvertible

{
    return list.Count(x => x.Equals(eType));
}

The problem is that there is no explicit way to say "T must be an enum". Requiring T to be a value type, and implement IComparable, IFormattable, and IConvertible, eliminates many (but not all) non-enum types.