What is HttpException Class in C#?

Question

ICSM Computer · Answer

The HttpException class in ASP.NET represents errors that occur 
during the processing of HTTP requests. It is part of the System.Web namespace and is used to handle
web-related runtime errors such as:
Missing files (404)Unauthorized access (401)Server errors (500)Custom application errors
Namespace
using System.Web;
Definition
public class HttpException : System.Runtime.InteropServices.ExternalException
HttpException inherits from ExternalException → 
SystemException → Exception.
Common Constructors
new HttpException()
new HttpException(string message)
new HttpException(string message, Exception innerException)
new HttpException(int httpCode, string message)
new HttpException(int httpCode, string message, Exception innerException)
Common Properties
Property
Description
Message
A description of the error
ErrorCode
The numeric error code (from ExternalException)
WebEventCode
ASP.NET health monitoring code
GetHttpCode()
Returns the HTTP status code (e.g., 404, 500)
GetHtmlErrorMessage()
Returns an HTML-formatted error string
Data
Gets a collection of key/value pairs that provide additional user-defined information about the exception.
ErrorCode
Gets the HRESULT of the error.
HelpLink
Gets or sets a link to the help file associated with this exception.
HResult
Gets or sets HRESULT, a coded numerical value that is assigned to a specific exception.
InnerException
Gets the 
Exception instance that caused the current exception.
Message
Gets a message that describes the current exception.
Source
Gets or sets the name of the application or the object that causes the error.
StackTrace
Gets a string representation of the immediate frames on the call stack.
TargetSite
Gets the method that throws the current exception.
WebEventCode
Gets the event codes that are associated with the HTTP exception.
Example: Throwing a 404 Not Found
throw new HttpException(404, "Page Not Found");
This throws a 404 error and can trigger a custom error page if configured.
Example: Throwing a 500 Internal Server Error
try
{
    // Some code that fails
}
catch (Exception ex)
{
    throw new HttpException(500, "Internal server error", ex);
}
Using in Custom Error Handling
In Global.asax.cs:
protected void Application_Error()
{
    Exception ex = Server.GetLastError();
    HttpException httpEx = ex as HttpException;
    int httpCode = httpEx != null ? httpEx.GetHttpCode() : 500;
    if (httpCode == 404)
    {
        Response.Redirect("~/Error/NotFound");
    }
    else
    {
        Response.Redirect("~/Error/ServerError");
    }
}
When to Use HttpException
To signal HTTP-specific errors in your app logic.To wrap lower-level exceptions in web-friendly messages.When integrating with ASP.NET error handling or custom error pages.To log and categorize errors by HTTP code (404, 403, etc.).
Summary Table
Feature
Example
Throw 404
throw new HttpException(404, "Not Found")
Throw with inner exception
throw new HttpException(500, "Server Error", ex)
Get status code
httpEx.GetHttpCode()
Use in Application_Error
For centralized error redirection
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What is HttpException Class in C#?

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Namespace

Definition

Common Constructors

Common Properties

Example: Throwing a 404 Not Found

Example: Throwing a 500 Internal Server Error

Using in Custom Error Handling

When to Use `HttpException`

Summary Table

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Property	Description
`Message`	A description of the error
`ErrorCode`	The numeric error code (from ExternalException)
`WebEventCode`	ASP.NET health monitoring code
`GetHttpCode()`	Returns the HTTP status code (e.g., 404, 500)
`GetHtmlErrorMessage()`	Returns an HTML-formatted error string
Data	Gets a collection of key/value pairs that provide additional user-defined information about the exception.
ErrorCode	Gets the `HRESULT` of the error.
HelpLink	Gets or sets a link to the help file associated with this exception.
HResult	Gets or sets HRESULT, a coded numerical value that is assigned to a specific exception.
InnerException	Gets the Exception instance that caused the current exception.
Message	Gets a message that describes the current exception.
Source	Gets or sets the name of the application or the object that causes the error.
StackTrace	Gets a string representation of the immediate frames on the call stack.
TargetSite	Gets the method that throws the current exception.
WebEventCode	Gets the event codes that are associated with the HTTP exception.

Feature	Example
Throw 404	`throw new HttpException(404, "Not Found")`
Throw with inner exception	`throw new HttpException(500, "Server Error", ex)`
Get status code	`httpEx.GetHttpCode()`
Use in `Application_Error`	For centralized error redirection