Jak zamienic string na select w LINQ?

using (CSharpCodeProvider foo = new CSharpCodeProvider()) {
    string s = "(sam.BMK_SU + sam.BMK_AEP) * 1.5 + 10";
    var assembly = foo.CompileAssemblyFromSource(
        new System.CodeDom.Compiler.CompilerParameters() { 
            GenerateInMemory = true
        },
        @"public class DynamicClass {
            // to /nadal/ nie zadziała, musisz jakoś przekazać BdeDb albo Kontext.
            // najlepiej w parametrze, o ile nie jest statyczna
            public string Execute() {
                return (from x in BdeDb.Kontext.TbMachine
                    where blabla
                    select " + s + @"); 
            }
        }"
    );

    var type = assembly.CompiledAssembly.GetType("DynamicClass");
    var instance = Activator.CreateInstance(type);
    var output = type.GetMethod("Execute").Invoke(instance, new object[0]);
}

 
          //test         
         IQueryable<Data1> baseQuery = (from c in ctx.Kontext.Data1 select c);
         IQueryable <Data1> whereClauseQuery = whereMachine( baseQuery, machine );

         List<Data1> sapListe = whereClauseQuery.ToList();
         
         //testowe
         string s = "((BMK_SU + BMK_AEP) * 1.5 + 10)+)";
         string s1 = "(BMK_SU + BMK_AEP) * 1.5 + 10";
         //def typ direct? 
         s1 = "1.0*(" + s1 + ")";

         IQueryable<Data2> samQuery = (from c in ctx.Kontext.Data2 select c);
         var rs = selectStatement( samQuery, s1, data2var );

        // double l1 = rs.SingleOrDefault();

         return sapWorkerExtensionsObject;
      }

      private dynamic whereMaschine( dynamic query, int machine )
      {
         string whereMaschine = "it.Machine == " + machine.ToString();
         var returnQuery = (IQueryable<object>)query;
         //test
         var query2 = DynamicQueryable.Where( query, whereMachine );
         
       return query2;
      }

      private dynamic selectStatement( dynamic query, string expression, Data2 data2var )
      {
         
         int machine = data2var.Machine;
         string au = data2var .Au;
         string ar = data2var.Ar;
                 
          //test where string
         string whereMaschine = "it.Machine == " + machine.ToString() + " && it.Au == " + "\""+ au + "\"";// + " && it.Ar == " + ar;
         var q3 = DynamicQueryable.Where( query, whereMachine );
         
         //test select string
         q3 = DynamicQueryable.Select( q3, expression );
         return q3;
      }

      private dynamic whereMaschine( dynamic query, int machine )
      {
         string whereMaschine = "it.Machine == " + machine.ToString();
         var returnQuery = (IQueryable<object>)query;
         //test
         var query2 = DynamicQueryable.Where( query, whereMachine );
 
       return query2;
      }

var query = ...;
string m = machine.ToString();
var query2 = query.Where(it => it == m);