已经掌握了在出现错误的情况下如何打破循环

本文关键字：情况下 何打破 循环 错误 掌握 | 更新日期: 2023-09-27 18:19:57

Q:

如果在事件中发现异常，我想中断循环。

代码：

XmlDocument x = new XmlDocument();
x.Load(targetFileName);
XmlReaderSettings settings = new XmlReaderSettings();
settings.CloseInput = true;
settings.ValidationEventHandler += Handler;
settings.ValidationType = ValidationType.Schema;
settings.Schemas.Add(null,System.Web.HttpContext.Current.Server.MapPath("~/importSchema/IntialSchema.xsd"));
settings.ValidationFlags =
     XmlSchemaValidationFlags.ReportValidationWarnings |
XmlSchemaValidationFlags.ProcessIdentityConstraints |
XmlSchemaValidationFlags.ProcessInlineSchema |
XmlSchemaValidationFlags.ProcessSchemaLocation;
using (StreamReader str_reader = new StreamReader(targetFileName))
{
    using (XmlReader validatingReader = XmlReader.Create(str_reader, settings))
    {
        while (validatingReader.Read())
        {
            //I wanna to break this loop if there is some caught error .
        }
    }
}

private static void Handler(object sender, ValidationEventArgs e)
{
    if (e.Severity == XmlSeverityType.Error || e.Severity == XmlSeverityType.Warning)
    {
        try
        {
            throw new Exception(
                 String.Format("Line: {0}, Position: {1} '"{2}'"",
                     e.Exception.LineNumber, e.Exception.LinePosition, e.Exception.Message));
        }
        catch (Exception ee)
        {
            Common.ErrMappingForInformix.WriteLog(ee.Message);
            ScheduleForm sf = new ScheduleForm();
            sf.ShowStatus("Error,Invalid xml file", "error", "", 1);
        }
    }
}

#编辑1:

XmlDocument x = new XmlDocument();
x.Load(targetFileName);
XmlReaderSettings settings = new XmlReaderSettings();
settings.CloseInput = true;
settings.ValidationEventHandler += (senderValidation, ee) =>
{
    if (ee.Severity == XmlSeverityType.Error || ee.Severity == XmlSeverityType.Warning)
    {
        try
        {
            this.validationFailed = true;
            throw new Exception(
                 String.Format("Line: {0}, Position: {1} '"{2}'"",
                     ee.Exception.LineNumber, ee.Exception.LinePosition, ee.Exception.Message));
        }
        catch (Exception ex)
        {
            Common.ErrMappingForInformix.WriteLog(ex.Message);
            this.ShowStatus("Error", "error", "", 1);
        }
    }
};
settings.ValidationType = ValidationType.Schema;
settings.Schemas.Add(null, System.Web.HttpContext.Current.Server.MapPath("~/importSchema/IntialSchema.xsd"));
settings.ValidationFlags =
     XmlSchemaValidationFlags.ReportValidationWarnings |
XmlSchemaValidationFlags.ProcessIdentityConstraints |
XmlSchemaValidationFlags.ProcessInlineSchema |
XmlSchemaValidationFlags.ProcessSchemaLocation;
using (StreamReader str_reader = new StreamReader(targetFileName))
{
    using (XmlReader validatingReader = XmlReader.Create(str_reader, settings))
    {
        while (validatingReader.Read())
        {
            //Loop through the document
            if (validationFailed)
            {
                break;
            }
        }
    }
}

它中断了循环，但不执行事件处理程序。

已经掌握了在出现错误的情况下如何打破循环

您可以设置一个标志来指示Handler方法中存在错误，然后检测该标志，如果已设置则使用break;。

在这种情况下，验证处理程序最好使用内联匿名委托，这样就不需要向包含方法的类中添加新的成员变量。（如果类仅处理XML读取/验证，则添加成员变量也没那么糟糕）

编辑：匿名内联委托意味着您可以添加一个事件处理程序，基本上不必在单独的方法中。例如：

bool validationFailed = false; // outside of the handler
settings.ValidationEventHandler += (sender, e) =>
{
    if (e.Severity == XmlS....
    // set validationFailed = true; in here to signal failure
};
// then detect validationFailed being true to know if/when to break;

我只需在处理程序中抛出异常，并在捕获它时中断控制流。但是，也要避免抛出过于通用的异常类型：最好使用自定义异常：

class XmlValidationFailedException : Exception {
   public XmlValidationFailedException(string message, Exception innerException) : base(message, innerException) {}
   // as per Kieren's comment, make sure this exception type is defined according to best practices
}

private static void Handler(object sender, ValidationEventArgs e)
{
    if (e.Severity == XmlSeverityType.Error || e.Severity == XmlSeverityType.Warning)
    {
        string message = String.Format("Line: {0}, Position: {1} '"{2}'"",
                     e.Exception.LineNumber, e.Exception.LinePosition, e.Exception.Message)
        throw new XmlValidationFailedException(message);
    }

然后你的循环可以变成这样：

try
{
   while (validatingReader.Read())
   {
       // do logic
   }
}
catch (XmlValidationException ex)
{
    // handle the error (log, show, ...) 
    return;
}
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