[Solved]-linq grouping by custom class-LINQ,C#

var keyDictionary = new Dictionary<string, IEnumerable<string>>();
keyDictionary.Add("Table1", new List<string> {"Group", "Position"});

var dt = new DataTable("Table1");
dt.Columns.AddRange(new [] { new DataColumn("Id", typeof(int)), new DataColumn("Group", typeof(string)), new DataColumn("Position", typeof(string)), new DataColumn("Name", typeof(string))});
var rowItemArrays = new [] { new object[] { 1, "Alpha", "Left", "Bob" }, new object[] { 2, "Alpha", "Right", "Mary"}, new object[] { 3, "Beta", "Right", "Bill"}, new object[] { 4, "Alpha", "Right", "Larry"}};
rowItemArrays.ToList().ForEach(i => dt.Rows.Add(i));

Func<DataRow, string> GetKeys = (dataRow) => string.Join("", keyDictionary[dataRow.Table.TableName].Select(key => dataRow[key].ToString()).ToArray());

var a = dt.AsEnumerable().GroupBy(GetKeys);

This is best logic you can try my friend, we have lot of studies regarding this, so what answer i have written is the logic given by my professor

This is cribbed from the help files and something I haven't implemented, but should work. The problem is that you need a single class for it to compare and it uses both ToString and GetHashCode in the comparison (which is why your dictionary idea didn't work, it isn't comparing the elements of the dictionary, it's comparing the ToString and GetHashCode of it). Have GetKey return the following class and populate the keyBag of the class with your Dictionary from above:

class PortableKey
{
    public Dictionary<string, object> keyBag { get; set; }

    public PortableKey(Dictionary<string, object> Keys)
    {
        this.keyBag = Keys;
    }

    public override bool Equals(object obj)
    {
        PortableKey other = (PortableKey)obj;
        foreach (KeyValuePair<string, object> key in keyBag)
        {
            if (other.keyBag[key.Key] != key.Value) return false;
        }
        return true;
    }

    public override int GetHashCode()
    {
        // hashCodes is an array of integers represented as strings. { "1", "4", etc. }
        string[] hashCodes = keyBag.Select(k => k.Value.GetHashCode().ToString()).ToArray();
        // hash is the Hash Codes all joined in a single string. "1,4,etc."
        string hash = string.Join(",", hashCodes);
        // returns a single hash code for the combined hash. 
        // Note, this is not guaranteed unique, nor is it intended to be so.
        return hash.GetHashCode();
    }
    public override string ToString()
    {
        string[] values = keyBag.Select(k => k.Value.ToString()).ToArray();
        return string.Join(",", values);
    }
}