c# - Dropdown value coming blank but still going in IF condition -

while submitting form, not selecting value dropdownlist , checking condition as

if (request.form["cmbnextuser"] != session["userid"].tostring() || request.form["cmbnextuser"] != null || request.form["cmbnextuser"] != "")         {             transfermail();         } 

so, while debugging value comes below.

the value coming blank still going in if condition

1. condition 1 causing since comparing value

    request.form["cmbnextuser"] != session["userid"].tostring()  

   i.e "" != session["userid"].tostring() evaluated ture thats why it executing if block.

2. change code this

   if (!string.isnullorempty(request.form["cmbnextuser"]) || request.form["cmbnextuser"] != session["userid"].tostring() ) {     transfermail(); }