Currently in C#, we need to first declare a variable before we pass it as an out parameter to a method. You can use a var while declaration if you initialize them in the same line, but when you don't want to initialize explicitly, you must declare them, specifying the full type:

    // predeclaration of 'out' variable was mandatory 
    int result; // or, var result = 0; 
    string value = "125"; 
 
    int.TryParse(value, out result); 
 
    Console.WriteLine("The result is: " + result); 

In C# 7.0, the out variables can be declared right at the point where they are passed as an out parameter to a method. You can now directly write int.TryParse(value, out int result); and get the value of the out parameter, to use it in the scope of the enclosing block:

    static void Main(string[] args) 
    { 
      string value = "125"; 
      int.TryParse(value, out int result); 
      Console.WriteLine("Result:  " + result); 
    } 

You can also use var instead of a strong type declaration, like int.TryParse(value, out var result);, and the compiler will define it properly:

    static void Main(string[] args) 
    { 
      string value = "125"; 
      int.TryParse(value, out var result); 
      Console.WriteLine("Result:  " + result); 
    } 

If you have already written code in the existing way of declaration before passing the out parameter to a method, Visual Studio 2017 will allow you to leverage this new feature of C# 7.0 from the light bulb icon:

From the popup, you can fix all the similar occurrences, in the current document, the entire project, or at the solution level, by clicking the links highlighted as shown in the preceding screenshot.