Not able to show tooltip value from resource file

I have developed one visual studio add-in in C#. Where hard coded string we are moving to resource file into two projects(1)under properties - resx file 2)we have some other project called resoures - resx file)
for example :
string str="Hello";
When I right click on it we are displaying menu item named Add Resource String. When I clicked on it I am chahging the value of "Hello" to JFramework.GetString(Resources.Key123)
so Now my string becomes
String str = JFramework.GetString(Resources.Key123);

Where I mousehover on Key123 I should get Hello as tooltip .

HOw can I do this. Please help me out.