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Home Interviews What is HttpException Class in C#? – MindStick
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ICSM Computer
ICSM Computer 05 May 2025
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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:

  1. Missing files (404)
  2. Unauthorized access (401)
  3. Server errors (500)
  4. 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

  1. To signal HTTP-specific errors in your app logic.
  2. To wrap lower-level exceptions in web-friendly messages.
  3. When integrating with ASP.NET error handling or custom error pages.
  4. 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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