Using keyword plays a vital role in improving the performance of Garbage Collection.
using for namespace means that the types from the imported namespace will be referenced in code
Disposemethod gets invoked
Generally Using key word we are using to add namespaces in the class. Using that all the classes, interfaces and abstract classes and their methods and properties available in the current class. we can declare namespace as given below.
I hope it gives you better understanding of using keyword in C#.