Check out example codes for "c# group array based on first character". It will help you in understanding the concepts better.

Code Example 1

Select().GroupBy(x => x.Name.Substring(0,1).ToUpper(), 
        (alphabet, subList) => new { 
          Alphabet = alphabet, 
          SubList = subList.OrderBy(x => x.Name).ToList() 
        }).OrderBy(x => x.Alphabet);

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