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C# 捕获多个异常（开发人员如何使用）

发布 2024年六月6日

处理异常在C#中正确地操作是至关重要的。本教程向您展示如何使用带有多个 catch 子句的 try-catch 块。我们将介绍如何捕获多种异常类型、使用异常筛选器，确保资源最终被清理。目标是帮助您构建健壮且容错的C#应用程序。

通过学习捕获多种类型的异常，您可以针对特定问题量身定制响应，从而提高程序的可靠性。我们还将讨论如何使用 when 关键字为catch块应用条件，从而实现更精确的错误处理。

本指南将为您提供在编码项目中顺利捕捉异常并处理常见和复杂错误的方法。我们还将探索IronPDF在处理异常情况时。

什么是异常处理？

在C#中，异常处理是一种用于处理运行时错误、防止程序突然终止以及在程序执行过程中管理意外情况的方法。异常处理的核心组件包括 try、catch 和 finally 块。

C#中Try-Catch的基本结构

try 块包含可能会引发异常的代码，而 catch 块负责处理异常（如果发生）。 finally 代码块是可选的，并且在 try 和 catch 代码块之后执行，无论是否抛出了异常。这是一个简单的结构：

try {
    // Code that may throw an exception
}
catch (Exception e) {
    // Code to handle the exception
}
finally {
    // Code that executes after try and catch, regardless of an exception
}

try {
    // Code that may throw an exception
}
catch (Exception e) {
    // Code to handle the exception
}
finally {
    // Code that executes after try and catch, regardless of an exception
}

Try
	' Code that may throw an exception
Catch e As Exception
	' Code to handle the exception
Finally
	' Code that executes after try and catch, regardless of an exception
End Try

VB C#

捕获多个异常

在现实应用中，单个操作可能会抛出各种类型的异常。为了解决这个问题，C#允许您为单个try块定义多个catch块。每个 catch 块可以指定不同的异常类型来处理所有异常。

为什么捕获多个异常？

捕获多个异常对于详细的错误处理至关重要，其中操作取决于发生的具体错误。它使开发人员能够根据特定错误的上下文，以适当的方式处理每个异常。

如何实现多个捕获块

以下是如何实现单个捕获块来捕获多种异常类型的示例：

try {
    // Code that may throw multiple types of exceptions
    int[] numbers = {1, 2, 3};
    Console.WriteLine(numbers[5]); // This will throw an IndexOutOfRangeException
}
catch (IndexOutOfRangeException ex) {
    Console.WriteLine("An index was out of range: " + ex.Message);
}
catch (DivideByZeroException ex) {
    Console.WriteLine("Can't divide by Zero: " + ex.Message);
}
catch (Exception ex) {
    Console.WriteLine("Error: " + ex.Message);
}

try {
    // Code that may throw multiple types of exceptions
    int[] numbers = {1, 2, 3};
    Console.WriteLine(numbers[5]); // This will throw an IndexOutOfRangeException
}
catch (IndexOutOfRangeException ex) {
    Console.WriteLine("An index was out of range: " + ex.Message);
}
catch (DivideByZeroException ex) {
    Console.WriteLine("Can't divide by Zero: " + ex.Message);
}
catch (Exception ex) {
    Console.WriteLine("Error: " + ex.Message);
}

Try
	' Code that may throw multiple types of exceptions
	Dim numbers() As Integer = {1, 2, 3}
	Console.WriteLine(numbers(5)) ' This will throw an IndexOutOfRangeException
Catch ex As IndexOutOfRangeException
	Console.WriteLine("An index was out of range: " & ex.Message)
Catch ex As DivideByZeroException
	Console.WriteLine("Can't divide by Zero: " & ex.Message)
Catch ex As Exception
	Console.WriteLine("Error: " & ex.Message)
End Try

VB C#

在此代码中，特定的异常如 IndexOutOfRangeException 和 DivideByZeroException 被各自的 catch 块捕获。任何其他类型的异常都由通用的 Exception 捕获块捕获。

使用带有 When 关键字的异常过滤器

C# 还支持异常筛选器，允许您在 catch 块中指定条件。该功能使用 when 关键字根据运行时评估的条件提供更精确的异常捕获控制。

以下是如何使用 when 关键字添加异常过滤器的方法：

try {
    // Code that may throw an exception
    throw new InvalidOperationException("Invalid operation occurred", new Exception("Inner exception"));
}
catch (Exception ex) when (ex.InnerException != null) {
    Console.WriteLine("Exception with inner exception caught: " + ex.Message);
}
catch (Exception ex) {
    Console.WriteLine("Exception caught: " + ex.Message);
}

try {
    // Code that may throw an exception
    throw new InvalidOperationException("Invalid operation occurred", new Exception("Inner exception"));
}
catch (Exception ex) when (ex.InnerException != null) {
    Console.WriteLine("Exception with inner exception caught: " + ex.Message);
}
catch (Exception ex) {
    Console.WriteLine("Exception caught: " + ex.Message);
}

Try
	' Code that may throw an exception
	Throw New InvalidOperationException("Invalid operation occurred", New Exception("Inner exception"))
Catch ex As Exception When ex.InnerException IsNot Nothing
	Console.WriteLine("Exception with inner exception caught: " & ex.Message)
Catch ex As Exception
	Console.WriteLine("Exception caught: " & ex.Message)
End Try

VB C#

最终块的作用

finally 块用于在 try 和任何 catch 块完成后执行代码。它对于清理资源非常有用，比如关闭文件流或数据库连接，无论是否发生异常。

try {
    // Code that might throw an exception
}
catch (Exception e) {
    // Handle the exception
}
finally {
    // Cleanup code, executed after try/catch
    Console.WriteLine("Cleanup code runs here.");
}

try {
    // Code that might throw an exception
}
catch (Exception e) {
    // Handle the exception
}
finally {
    // Cleanup code, executed after try/catch
    Console.WriteLine("Cleanup code runs here.");
}

Try
	' Code that might throw an exception
Catch e As Exception
	' Handle the exception
Finally
	' Cleanup code, executed after try/catch
	Console.WriteLine("Cleanup code runs here.")
End Try

VB C#

IronPDF 介绍

IronPDF是为在 .NET 应用程序中工作的 C# 开发人员设计的综合库。它帮助开发人员操作、管理和直接从 HTML 创建 PDF 文件. 它不需要外部依赖来运行。

您可以在无需使用和安装Adobe Acrobat的情况下执行任何PDF操作。 IronPDF 支持多种 PDF 功能，例如编辑、合并、拆分，以及通过加密和数字签名保护 PDF 文件。开发人员可以在多种应用程序类型中使用IronPDF，包括Web应用程序、桌面应用程序和服务。

互连：

IronPDF的关键功能是转换HTML 转 PDF, 保留布局和样式。它非常适合从网页内容生成PDF，无论是用于报告、发票还是文档。 HTML文件、URL和HTML字符串都可以转换为PDF文件。

using IronPdf;

class Program
{
    static void Main(string[] args)
    {
        var renderer = new ChromePdfRenderer();

        // 1. Convert HTML String to PDF
        var htmlContent = "<h1>Hello, IronPDF!</h1><p>This is a PDF from an HTML string.</p>";
        var pdfFromHtmlString = renderer.RenderHtmlAsPdf(htmlContent);
        pdfFromHtmlString.SaveAs("HTMLStringToPDF.pdf");

        // 2. Convert HTML File to PDF
        var htmlFilePath = "path_to_your_html_file.html"; // Specify the path to your HTML file
        var pdfFromHtmlFile = renderer.RenderHtmlFileAsPdf(htmlFilePath);
        pdfFromHtmlFile.SaveAs("HTMLFileToPDF.pdf");

        // 3. Convert URL to PDF
        var url = "http://ironpdf.com"; // Specify the URL
        var pdfFromUrl = renderer.RenderUrlAsPdf(url);
        pdfFromUrl.SaveAs("URLToPDF.pdf");
    }
}

using IronPdf;

class Program
{
    static void Main(string[] args)
    {
        var renderer = new ChromePdfRenderer();

        // 1. Convert HTML String to PDF
        var htmlContent = "<h1>Hello, IronPDF!</h1><p>This is a PDF from an HTML string.</p>";
        var pdfFromHtmlString = renderer.RenderHtmlAsPdf(htmlContent);
        pdfFromHtmlString.SaveAs("HTMLStringToPDF.pdf");

        // 2. Convert HTML File to PDF
        var htmlFilePath = "path_to_your_html_file.html"; // Specify the path to your HTML file
        var pdfFromHtmlFile = renderer.RenderHtmlFileAsPdf(htmlFilePath);
        pdfFromHtmlFile.SaveAs("HTMLFileToPDF.pdf");

        // 3. Convert URL to PDF
        var url = "http://ironpdf.com"; // Specify the URL
        var pdfFromUrl = renderer.RenderUrlAsPdf(url);
        pdfFromUrl.SaveAs("URLToPDF.pdf");
    }
}

Imports IronPdf

Friend Class Program
	Shared Sub Main(ByVal args() As String)
		Dim renderer = New ChromePdfRenderer()

		' 1. Convert HTML String to PDF
		Dim htmlContent = "<h1>Hello, IronPDF!</h1><p>This is a PDF from an HTML string.</p>"
		Dim pdfFromHtmlString = renderer.RenderHtmlAsPdf(htmlContent)
		pdfFromHtmlString.SaveAs("HTMLStringToPDF.pdf")

		' 2. Convert HTML File to PDF
		Dim htmlFilePath = "path_to_your_html_file.html" ' Specify the path to your HTML file
		Dim pdfFromHtmlFile = renderer.RenderHtmlFileAsPdf(htmlFilePath)
		pdfFromHtmlFile.SaveAs("HTMLFileToPDF.pdf")

		' 3. Convert URL to PDF
		Dim url = "http://ironpdf.com" ' Specify the URL
		Dim pdfFromUrl = renderer.RenderUrlAsPdf(url)
		pdfFromUrl.SaveAs("URLToPDF.pdf")
	End Sub
End Class

VB C#

代码示例

以下是一个使用IronPDF从HTML创建PDF的简单C#示例，并包含多种异常的错误处理。本例假设您已在项目中安装了IronPDF。在 NuGet 控制台中运行以下命令以安装 IronPDF：

Install-Package IronPdf

代码如下：

using IronPdf;
using System;
class Program
{
    static void Main(string[] args)
    {
        License.LicenseKey = "License-Key";
        var renderer = new ChromePdfRenderer();
        try
        {
            // Convert HTML to PDF
            var pdf = renderer.RenderHtmlAsPdf("<h1>Hello, World!</h1>");
            pdf.SaveAs("Exceptions.pdf");
            Console.WriteLine("PDF successfully created.");
        }
        catch (IronPdf.Exceptions.IronPdfProductException ex)
        {
            // Handle PDF generation errors
            Console.WriteLine("Failed to generate PDF: " + ex.Message);
        }
        catch (System.IO.IOException ex)
        {
            // Handle IO errors (e.g., disk I/O errors)
            Console.WriteLine("IO Exception: " + ex.Message);
        }
        catch (Exception ex)
        {
            // Handle other errors
            Console.WriteLine("Error" + ex.Message);
        }
    }
}

using IronPdf;
using System;
class Program
{
    static void Main(string[] args)
    {
        License.LicenseKey = "License-Key";
        var renderer = new ChromePdfRenderer();
        try
        {
            // Convert HTML to PDF
            var pdf = renderer.RenderHtmlAsPdf("<h1>Hello, World!</h1>");
            pdf.SaveAs("Exceptions.pdf");
            Console.WriteLine("PDF successfully created.");
        }
        catch (IronPdf.Exceptions.IronPdfProductException ex)
        {
            // Handle PDF generation errors
            Console.WriteLine("Failed to generate PDF: " + ex.Message);
        }
        catch (System.IO.IOException ex)
        {
            // Handle IO errors (e.g., disk I/O errors)
            Console.WriteLine("IO Exception: " + ex.Message);
        }
        catch (Exception ex)
        {
            // Handle other errors
            Console.WriteLine("Error" + ex.Message);
        }
    }
}

Imports IronPdf
Imports System
Friend Class Program
	Shared Sub Main(ByVal args() As String)
		License.LicenseKey = "License-Key"
		Dim renderer = New ChromePdfRenderer()
		Try
			' Convert HTML to PDF
			Dim pdf = renderer.RenderHtmlAsPdf("<h1>Hello, World!</h1>")
			pdf.SaveAs("Exceptions.pdf")
			Console.WriteLine("PDF successfully created.")
		Catch ex As IronPdf.Exceptions.IronPdfProductException
			' Handle PDF generation errors
			Console.WriteLine("Failed to generate PDF: " & ex.Message)
		Catch ex As System.IO.IOException
			' Handle IO errors (e.g., disk I/O errors)
			Console.WriteLine("IO Exception: " & ex.Message)
		Catch ex As Exception
			' Handle other errors
			Console.WriteLine("Error" & ex.Message)
		End Try
	End Sub
End Class

VB C#

当我们运行此代码时，它在命令行中显示此消息。

C# 捕捉多重异常（开发人员如何操作）：图 1