You should notice that you are passing a class to the CurrentValues.Add
method
so the only thing you have to change is this:
put ParameterDiscreteValue v1 = new ParameterDiscreteValue();
to the loop
ParameterField f1 = CrystalReportViewer1.ParameterFieldInfo["Emp Id"];
string LBL1 = Request.QueryString["LBL1"].ToString();
string[] LBL1split = LBL1.Split(',');
foreach (string item in LBL1split)
{
ParameterDiscreteValue v1 = new ParameterDiscreteValue();
v1.Value = item;
f1.CurrentValues.Add(v1);
}