c# - Casting into grouping row

Question

I dont know why i am getting the following exception how can I cast into grouping Row ? What does grouping row means

Answer 1

Quick answer: change the code to

foreach(var InvoiceHeader in InvoiceHeadercollection)

The linq code has generated a new class, which you can think of like this:

class AutoGeneratedClass :  IEnumerable<DataRow>
{
    public string Key { get; }  // The InvoiceAccount field
}

(It's not called "AutoGeneratedClass"; I'm just using that so it follows the syntax we know). Because there's no name for this automatically generated class, you have to use "var".