handle Null in sql server

Concat Function in SQL Server
 
When i add null with any data type either it is int , varchar , char , nvarchar , It re return the null values always , my query is that instead of null value i want the result excluding the null values for example
 
So i need a query which will return the result without null value
 
1st - Select Convert(nvarchar(20) , 1) + Null
Output = Null
 
My required result 1
 
2nd - Select 'A' + null
Null
 

My required result should be A instead of Null