{"id":1356,"date":"2023-04-03T12:22:38","date_gmt":"2023-04-03T05:22:38","guid":{"rendered":"https:\/\/csharptutorial.net\/?page_id=1356"},"modified":"2023-04-03T12:25:17","modified_gmt":"2023-04-03T05:25:17","slug":"csharp-rethrow-exception","status":"publish","type":"page","link":"https:\/\/www.csharptutorial.net\/csharp-tutorial\/csharp-rethrow-exception\/","title":{"rendered":"C# Rethrow Exceptions"},"content":{"rendered":"\n

Summary<\/strong>: in this tutorial, you’ll learn how to rethrow an exception in C# using the throw<\/code> statement.<\/p>\n\n\n\n

When to rethrow exceptions in C# <\/h2>\n\n\n\n

In C#, you can use the try...catch<\/a><\/code> block to catch an exception in the try<\/code> block and handle it accordingly in the catch<\/code> block.<\/p>\n\n\n\n

In some cases, you may want to re-throw an exception after you have caught it in the catch<\/code> block.<\/p>\n\n\n\n

This can be useful if you need to log the exception first and then propagate it up the call stack, which you will handle in another catch<\/code> block.<\/p>\n\n\n\n

The following illustrates how to rethrow an exception:<\/p>\n\n\n

try<\/span>\n{\n    \/\/ Some code that might throw an exception<\/span>\n}\ncatch<\/span> (Exception ex)\n{\n    \/\/ Handle the exception<\/span>\n    Console.WriteLine($\"An exception occurred: {ex.Message}<\/span>\"<\/span>);\n\n    \/\/ Rethrow the exception<\/span>\n    throw<\/span>;\n}<\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
In this syntax, the code in the try<\/code> block might throw an exception. If an exception occurs, we handle it in the catch<\/code> block.<\/p>\n\n\n\n
In the catch<\/code> block, we handle the exception by showing a message to the console and use rethrow it using the throw<\/code> statement.<\/p>\n\n\n\n
C# rethrow exceptions example<\/h2>\n\n\n\n
The following example demonstrates how to rethrow an exception using the throw<\/code> statement:<\/p>\n\n\n
static<\/span> float<\/span> Divide<\/span>(int<\/span> a, int<\/span> b<\/span>)<\/span>\n{\n    return<\/span> a \/ b;\n}\n\ntry<\/span>\n{\n    var<\/span> result = Divide(10<\/span>, 0<\/span>);\n}\ncatch<\/span> (DivideByZeroException ex)\n{\n    Console.WriteLine(ex.Message);\n    \/\/ rethrow the exception<\/span>\n    throw<\/span>;\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 the Divide()<\/code> method that returns the division of two integers.<\/p>\n\n\n\n
Second, divide 10 by zero using the Divide<\/code> method. In the catch block, we log the exception message to the console and rethrow the same DivideByZeroException<\/code> exception.<\/p>\n\n\n\n
Catching and rethrowing another exception<\/h2>\n\n\n\n
Sometimes, you want to handle an exception and wrap it in a new exception, and propagate the new exception up the call stack.<\/p>\n\n\n\n
To do that you use the throw<\/code> statement with the new exception and you pass the original exception to the inner exception parameter of the new exception. For example:<\/p>\n\n\n
static<\/span> float<\/span> Divide<\/span>(int<\/span> a, int<\/span> b<\/span>)<\/span>\n{\n    return<\/span> a \/ b;\n}\n\n\ntry<\/span>\n{\n    var<\/span> result = Divide(10<\/span>, 0<\/span>);\n}\ncatch<\/span> (DivideByZeroException ex)\n{\n    Console.WriteLine(ex.Message);\n\n    \/\/ rethrow the exception<\/span>\n    throw<\/span> new<\/span> ArithmeticException(ex.Message, ex);\n}<\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
In this example, we log the message of the DivideByZeroException<\/code> exception to the console. <\/p>\n\n\n\n
Also, we wrap the DivideByZeroException<\/code><\/code> into a new ArithmeticException<\/code><\/code> exception by assigning the DivideByZeroException<\/code><\/code> exception to the InnerException<\/code> property of the ArithmeticException<\/code><\/code> exception.<\/p>\n\n\n\n
The following shows the ArithmeticException<\/code> with DivisionByZeroException<\/code> as the inner exception:<\/p>\n\n\n\n
\"\"<\/figure>\n\n\n\n
Summary<\/h2>\n\n\n\n
    \n
  • Rethrow an exception when you want to do something like logging before propagating the same exception up the call stack.<\/li>\n\n\n\n
  • Use the throw<\/code> statement to rethrow the same exception.<\/li>\n<\/ul>\n
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