what is the Linq query of this sql query

Its not as simple as just creating single LINQ statement, because you will actually need to create 3 statements.

An example is given here.

Personally I think the example is a little obtuse.

My example would be to create a specific type of the object you want to use.

public class CM_MT_REF_CODE
   {
       public Int32 NBRANCH_SL { get; set; }
       public Int32 NCM_SL { get; set; }
       public string CNAME { get; set; }
   }

Then create your initial element, add it to a list, do your query, then add the range to your list.

List<CM_MT_REF_CODE> results = new List<CM_MT_REF_CODE>();
var query = from CM_MT_REF_CODE c in table
            select c;
results.Add(new CM_MT_REF_CODE { CNAME = "<Select>" });
results.AddRange(query);

//use results