CODEWITHSUNDEEP
c#genericsextension-methods
goyaltushar92
goyaltushar92

Reputation: 348

unable to create generic extension method

I was trying to create a generic extension method using following code but it gives compile time error

public static class extentions<TSource, TResult>
{
    public static IEnumerable<TSource> GetWholeHerichy(this IEnumerable<TSource> source, Func<TSource, TResult> KeySelector, Func<TSource, TResult> FKeySelector, TResult KeyElementid)
    {
        var k = source.Where(a => EqualityComparer<TResult>.Default.Equals(KeyElementid, KeySelector(a))).ToList();
        while(true)
        {
            var nextLevel = source.Where(a => k.Select(b => KeySelector(b)).Contains(FKeySelector(a)) && ! k.Select(b => KeySelector(b)).Contains(KeySelector(a)));
            if (nextLevel == null || nextLevel.Count() < 1)
                break;
            k.AddRange(nextLevel);
        }
        return k.AsEnumerable();
    }
}

Error is

Error 1 Extension method must be defined in a non-generic static class

if i removes <TSource, TResult> from public static class extentions<TSource, TResult> to make class non-generic then TSource and TResult became undefined in whole class

Upvotes: 0

Views: 63

Answers (1)

xanatos
xanatos

Reputation: 111820

You must "move" the generic types in the method signature:

public static IEnumerable<TSource> GetWholeHerichy<TSource, TResult>(this IEnumerable<TSource> source, Func<TSource, TResult> KeySelector, Func<TSource, TResult> FKeySelector, TResult KeyElementid)

exactly like the various Enumerable.* methods.

Upvotes: 2

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