Unable to cast object of type 'd__6' to type 'System.Object[]'

Question

I'm trying to lazy load (extension with yield return) the rows in a 2D object array. I get the following error: c# Unable to cast object of type '<>d__6' to type 'System.Object[]'. The exception occurs on this line found in the `Parse` method: ``` yield return (TSource) conversion(o); ``` I don't understand why `C#` thinks the return value is `<>d__6` instead of `Object[]`. I normally program in `VB.NET` so I don't think I'm understanding the nuances of `C#`. What am I doing wrong? I looked at the other similar questions/answers but am still confused. ``` public static IEnumerable Parse(this object[,] array , Func, IEnumerable> conversion , int rowStart, int columnStart, int rowCount, int columnCount) { IEnumerable o = array.ForEachRow(rowStart, columnStart, rowCount, columnCount); yield return (TSource) conversion(o); } ``` ForEachRow method: ``` public static IEnumerable ForEachRow(this object[,] array, int rowStar…

Accepted Answer

`o` is an `IEnumerable`. `conversion(o)` is an `IEnumerable`. You are converting a sequence of objects into a sequence of `TSource` items. You then cast that `IEnumerable` to `TSource`. You're basically saying, "Treat this sequence of `TSource` items as a single `TSource` item." What the runtime is telling you is that, "I'm not allowed to treat that sequence of items as a `TSource` item, because that's not what it is. What you almost certainly want to actually do is just replace the last line with: ``` return conversion(o); ``` You have a sequence of `TSource` items, and that's exactly what you need to return. You were overthinking it by trying to use an iterator block. If you really, really want to use an iterator block, then you need to yield each item in the sequence, like this: ``` foreach (TSource item in conversion(o)) yield return item; ``` But why bother.

Unable to cast object of type '<>d__6' to type 'System.Object[]'

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