{"id":1377,"date":"2023-04-04T11:16:59","date_gmt":"2023-04-04T04:16:59","guid":{"rendered":"https:\/\/csharptutorial.net\/?page_id=1377"},"modified":"2023-04-04T11:17:01","modified_gmt":"2023-04-04T04:17:01","slug":"csharp-throw-exception","status":"publish","type":"page","link":"https:\/\/www.csharptutorial.net\/csharp-tutorial\/csharp-throw-exception\/","title":{"rendered":"C# throw"},"content":{"rendered":"\n

Summary<\/strong>: in this tutorial, you’ll learn how to use the C# throw<\/code> keyword to raise an exception in your application.<\/p>\n\n\n\n

Introduction to the C# throw keyword<\/h2>\n\n\n\n

The throw<\/code> keyword allows you to raise an exception. Here’s the syntax of how to use the throw<\/code> keyword: <\/p>\n\n\n

throw<\/span> exception;<\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
In this syntax, the exception<\/code> is an object that represents the exception that you want to raise. You can use any built-in exception class that is derived from the System.Exception<\/code> class. Also, you can raise a custom exception<\/a>, which will cover in the next tutorial.<\/p>\n\n\n\n
Typically, you use the throw<\/code> keyword with an if<\/a><\/code> statement to throw an exception once a certain condition is met:<\/p>\n\n\n
if<\/span> (condition)\r\n{\r\n    throw<\/span> exception;\r\n}<\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
Using the C# throw keyword to raise an exception example<\/h2>\n\n\n\n
The following program demonstrates how to use the throw<\/code> keyword to throw an ArgumentOutOfRangeException<\/code> exception:<\/p>\n\n\n
using<\/span> static<\/span> System.Console;\r\n\r\npublic<\/span> class<\/span> Circle<\/span>\r\n{\r\n    public<\/span> double<\/span> Radius\r\n    {\r\n        get<\/span>; set<\/span>;\r\n    }\r\n    public<\/span> Circle<\/span>(double<\/span> radius<\/span>)<\/span>\r\n    {\r\n        if<\/span> (radius <= 0<\/span>)\r\n        {\r\n            throw<\/span> new<\/span> ArgumentOutOfRangeException(\r\n                 nameof<\/span>(radius),\r\n                \"The radius should be positive\"<\/span>\r\n             );\r\n        }\r\n        Radius = radius;\r\n    }\r\n    public<\/span> double<\/span> GetArea<\/span>(<\/span>)<\/span> => Math.PI * Radius * Radius;\r\n\r\n}\r\n\r\nclass<\/span> Program<\/span>\r\n{\r\n    public<\/span> static<\/span> void<\/span> Main<\/span>(string<\/span>[] args<\/span>)<\/span>\r\n    {\r\n        WriteLine(\"Enter a radius:\"<\/span>);\r\n        var<\/span> input = ReadLine();\r\n        if<\/span> (input != null<\/span>)\r\n        {\r\n            var<\/span> radius = double<\/span>.Parse(input);\r\n            try<\/span>\r\n            {\r\n                var<\/span> circle = new<\/span> Circle(radius);\r\n                WriteLine($\"The area is {circle.GetArea():F2}<\/span>\"<\/span>);\r\n            }\r\n            catch<\/span> (ArgumentOutOfRangeException ex)\r\n            {\r\n                WriteLine(ex.Message);\r\n            }\r\n\r\n        }\r\n    }\r\n}<\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
How it works.<\/p>\n\n\n\n
First, define a class called Circle<\/code> that represents a circle with a given radius. <\/p>\n\n\n\n
In the Circle<\/code> class, we define a constructor that takes a double<\/code> value representing the radius of the circle. If the value of the radius is less than or equal to zero, we throw an ArgumentOutOfRangeException<\/code> with a custom error message using the throw<\/code> keyword.<\/p>\n\n\n\n
In the Circle<\/code> class, we also define a method GetArea()<\/code> that returns the area of the circle using the formula \u03c0r\u00b2.<\/p>\n\n\n\n
Second, prompt the user to enter a radius in the Main<\/code> method of the program.  <\/p>\n\n\n\n
The Main()<\/code> method:<\/p>\n\n\n\n
    \n
  • Reads the input from the console  <\/li>\n\n\n\n
  • Parses it to a double<\/code> <\/li>\n\n\n\n
  • Creates an instance of the Circle<\/code> class with the entered radius value <\/li>\n\n\n\n
  • Calls the GetArea()<\/code> method to calculate the area of the circle. <\/li>\n<\/ul>\n\n\n\n
    If the entered radius is not positive, the Main<\/code> method catches the ArgumentOutOfRangeException<\/code> exception raised by the constructor and displays the error message on the console.<\/p>\n\n\n\n
    The throw Expression<\/h2>\n\n\n\n
    Starting from C# 7.0, you can use the throw<\/code> keyword as an expression. This allows you to throw an exception inline, without having to define a separate variable. The syntax of the throw<\/code> expression is as follows:<\/p>\n\n\n
    throw<\/span> expression;<\/code><\/span>Code language:<\/span> JavaScript<\/span> (<\/span>javascript<\/span>)<\/span><\/small><\/pre>\n\n\n
    In this syntax, the expression<\/code> evaluates to an object derived from the System.Exception<\/code> class. For example, you can change the Circle<\/code> constructor in the previous example to the following:<\/p>\n\n\n
    public<\/span> Circle<\/span>(double<\/span> radius<\/span>)<\/span>\r\n{\r\n    Radius = radius > 0<\/span>\r\n                ? radius\r\n                : throw<\/span> new<\/span> ArgumentOutOfRangeException(\r\n                    nameof<\/span>(radius),\r\n                    \"The radius should be positive\"<\/span>\r\n                  );\r\n}<\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
    In this example, if the radius<\/code> is greater than zero, we assign it to the Radius<\/code> property. Otherwise, we throw the ArgumentOutOfRangeException<\/code> exception. This has the same effect as the previous example but is more concise.<\/p>\n\n\n\n
    Summary<\/h2>\n\n\n\n
      \n
    • Use the C# throw<\/code> keyword to raise an exception explicitly.<\/li>\n<\/ul>\n
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