LINQ - split a List into groups of 100, grouped by Customernumber,

Hello 

I am looking to split a List into groups of 100, grouped by Customernumber,

The below method has syntax errors.  I don't want one Customer information split up in two different groups. Should be included in the same split group.

private List<List<InvoiceLines>> Split(List<InvoiceLines> invoiceLines)
        {
            List<List<InvoiceLines>> MySplitInvoices =  invoiceLines.GroupBy(row => row.CustomerAccount).Select(c => new { Id = c.Key, list = c.ToList() })
                .Select((x, i) => new List<InvoiceLines> { Index = i, Value = x })
                .GroupBy(x => x.Index / 100)
                .Select(x => x.Select(v => v.Value).ToList())
                .ToList();

            return test;
        }

Below code Just works fine, except my list contains, customer Information. I don't want one Customer information split up in two different groups. Should be included in the same split group.

 private List<List<InvoiceLines>> Split(List<InvoiceLines> invoiceLines)
        {
            List<List<InvoiceLines>> SplitInvoices =  invoiceLines
                .Select((x, i) => new  { Index = i, Value = x })
                .GroupBy(x => x.Index / 100)
                .Select(x => x.Select(v => v.Value).ToList())
                .ToList();

            return test;
        }

Thank you