Fix To: The Out Parameter Must Be Assigned to Before Control Leaves the Current Method

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Introduction

• The out keyword causes arguments to be passed by reference.
• To use an out parameter, both the method definition and the calling method must explicitly use the out keyword.
• Although variables passed as out arguments do not have to be initialized before being passed, the called method is required to assign a value before the method returns.

Example

Simple Program to check whether the given character exists or not,

1. using System;  
2.   
3. class Program  
4. {  
5.     static void Main ( )  
6.     {  
7.         bool sharpsymbol; // Used as out parameter.  
8.         bool AndSymbol;  
9.         bool Paranthesis;  
10.         const string value = "& # @";// Used as input string.  
11.   
12.         CheckString ( value, out sharpsymbol, out AndSymbol, out Paranthesis );  
13.   
14.         Console.WriteLine ( value ); // Display value.  
15.         Console.Write ( "sharpsymbol: " ); // Display labels and bools.  
16.         Console.WriteLine ( sharpsymbol );  
17.         Console.Write ( "AndSymbol: " );  
18.         Console.WriteLine ( AndSymbol );  
19.         Console.Write ( "Paranthesis: " );  
20.         Console.WriteLine ( Paranthesis );  
21.         Console.ReadLine ( );  
22.     }  
23.   
24.     static void CheckString ( string value,  
25.     out bool sharpsymbol,  
26.     out bool AndSymbol,  
27.     out bool Paranthesis )  
28.     {  
29.         // Assign all out parameters to false.  
30.     
31.   
32.         sharpsymbol = AndSymbol = Paranthesis = false;  
33.   
34.         for(int i = 0; i < value.Length; i++)  
35.         {  
36.             switch(value[i])  
37.             {  
38.                 case '#':  
39.                     {  
40.                         sharpsymbol = true; // Set out parameter.  
41.                         break;  
42.                     }  
43.                 case '&':  
44.                     {  
45.                         AndSymbol = true; // Set out parameter.  
46.                         break;  
47.                     }  
48.                 case '(':  
49.                     {  
50.                         Paranthesis = false; // Set out parameter.  
51.                         break;  
52.                     }  
53.             }  
54.         }  
55.     }  
56. }  

Output

http://csharpcorner.mindcrackerinc.netdna-cdn.com/UploadFile/BlogImages/06232016021243AM/image001.jpg

When the Problem Occurs.

http://csharpcorner.mindcrackerinc.netdna-cdn.com/UploadFile/BlogImages/06232016021243AM/image002.jpg

Note 

In the above program, even though you assigned the out variable value inside the looping/case statement, if you don't assign any value in the method definition like the above snagit then you will get the following error:

http://csharpcorner.mindcrackerinc.netdna-cdn.com/UploadFile/BlogImages/06232016021243AM/image003.jpg

Conclusion

I hope the above information is useful for beginners, kindly let me know your thoughts.