I am trying to fetch the selected value of the listbox. When I actually try LstGroup1.SelectedItem I get the value { BoothID = \"4\", BoothName = \"HP\" }
You can always create a class called Booth to get the data in the Object Format. From My point of view Dynamic is not the right way of doing this. Once you have the Class Booth in the Solution you can run
Booth Booth1 = LstGroup1.SelectedItem as Booth;
string BoothID1 = Booth1.BoothID;