Query in foreach loop

public static string Jqufunc(int yearP)
{
	string res = "[";
	ProjectdbEntities a = new ProjectdbEntities();
	var b = a.Catg_type;
	foreach (var c in b)
	{

		res += "'" + c.Catg_type1 + "',";
	}
	res = res.Substring(0, res.Length - 1);
	res += "]";

	var allprogs = a.Program_type;
	string res2 = "[";
	foreach (var pr in allprogs)
	{
		res2 += "{name: '" + pr.Prog_name + "',";
		var allcats = a.Catg_type;
		res2 += "data:[";


		var query = (a.Std_info.Join(a.Catg_type, stdtable => stdtable.Catg_id,
		catg => catg.Catg_id, (stdtable, catg) => new {stdtable, catg})
		.Join(a.Program_type, t => t.stdtable.Prog_id, prog => prog.Prog_id, (t, prog) => new {t, prog})
		.Join(a.Year_info, t => t.t.stdtable.year_id, yea => yea.year_id, (t, yea) => new {t, yea})
		.Where(t=>t.t.t.stdtable.year_id==yearP)
		.GroupBy(
		t =>
		new { t.t.t.catg.Catg_type1, t.t.prog.Prog_name, t.yea.year, t.t.t.stdtable.Catg_id },
		t => t.t.t.stdtable)
		.Select(g => new
		{
			g.Key.Catg_type1,
			g.Key.Prog_name,
			g.Key.year,
			g.Key.Catg_id,
			total_students = g.Select(p=>p.Catg_id).Distinct().Count()
		})).ToList();
		res2 = res2.Substring(0, res2.Length - 1);
		foreach(var ab in res2)
		{
			res2 += query(yearP);
		}
	}
	res2 += "]";
	res2 += "},";
	return res + "*" + res2;

}