如果字符串为空，则跳过行

Question

如果字符串为空，我想跳过一行。

我尝试这样的：

public void ReadPostedData() 
{ 
    Sender = HttpContext.Current.Request.Form["MailFormSubmitter_sender"]; 
    Subject = HttpContext.Current.Request.Form["MailFormSubmitter_subject"];   
    Message = HttpContext.Current.Request.Form["Message"]; 
    PdfMessage = HttpContext.Current.Request.Form["PdfMessage"]; 

    string IsCheckPDfMailSubmit = HttpContext.Current.Request.Form["IsCheckedPDFMailForm"]; 
    if (IsCheckPDfMailSubmit == null || IsCheckPDfMailSubmit.Length == 0) 

     //string.IsNullOrEmpty(IsCheckPDfMailSubmit); 

    return IsCheckPDfMailSubmit == null; 

    IsCheckedPDFMailForm = IsCheckPDfMailSubmit.Equals("True", StringComparison.OrdinalIgnoreCase); 

    string v = HttpContext.Current.Request.Form["MailFormSubmitter_includeoverviewpdf"]; 
    IncludeOverviewPdf = v.Equals("true,false", StringComparison.Ordinal) ? true : false; 
    // http://forums.asp.net/t/1314753.aspx 

    ApplicantMailNodeSelectors[0] = HttpContext.Current.Request.Form["MailFormSubmitter_applicantemailaddress1"]; 
    ApplicantMailNodeSelectors[1] = HttpContext.Current.Request.Form["MailFormSubmitter_applicantemailaddress2"]; 
    ApplicantMailNodeSelectors[2] = HttpContext.Current.Request.Form["MailFormSubmitter_applicantemailaddress3"]; 
} 

它是关于这一行：

if (IsCheckPDfMailSubmit == null || IsCheckPDfMailSubmit.Length == 0) 

如果是空，不执行该行：

IsCheckedPDFMailForm = IsCheckPDfMailSubmit.Equals("True", StringComparison.OrdinalIgnoreCase); 

我试试吧像这样：

return IsCheckPDfMailSubmit == null; 

但后来我得到以下错误：

Error 6 Since 'Seneca.SfsLib.Connectors.MailFormSubmitterModel.ReadPostedData()' returns void, a return keyword must not be followed by an object expression

那么怎么跳过？

Answer 1

如果你想这取决于在if语句中的条件从功能退出，你只使用return;时，该方法具有void的返回类型：

if (IsCheckPDfMailSubmit == null || IsCheckPDfMailSubmit.Length == 0) { 
    return; 
} 

或者，而不是退出在函数的中间，可以反转条件并将其余代码放在if声明中：

if (!(IsCheckPDfMailSubmit == null || IsCheckPDfMailSubmit.Length == 0)) { 
    // ... 
    // rest of the code in the method 
    // ... 
} 

如果你只是想跳过以下线路，但该方法的代码的其余部分恢复，反转的条件，并把该行的if声明：

if (!(IsCheckPDfMailSubmit == null || IsCheckPDfMailSubmit.Length == 0)) { 
    IsCheckedPDFMailForm = IsCheckPDfMailSubmit.Equals("True", StringComparison.OrdinalIgnoreCase); 
} 

Answer 2

public void ReadPostedData() 
{ 
    Sender = HttpContext.Current.Request.Form["MailFormSubmitter_sender"]; 
    Subject = HttpContext.Current.Request.Form["MailFormSubmitter_subject"];   
    Message = HttpContext.Current.Request.Form["Message"]; 
    PdfMessage = HttpContext.Current.Request.Form["PdfMessage"]; 

    string IsCheckPDfMailSubmit = HttpContext.Current.Request.Form["IsCheckedPDFMailForm"]; 
    if (IsCheckPDfMailSubmit != null) { 
     if(IsCheckPDfMailSubmit.Length > 0){ 
      IsCheckedPDFMailForm = IsCheckPDfMailSubmit.Equals("True", StringComparison.OrdinalIgnoreCase); 
     } 
    } 





    string v = HttpContext.Current.Request.Form["MailFormSubmitter_includeoverviewpdf"]; 
    IncludeOverviewPdf = v.Equals("true,false", StringComparison.Ordinal) ? true : false; 
// http://forums.asp.net/t/1314753.aspx 

    ApplicantMailNodeSelectors[0] = HttpContext.Current.Request.Form["MailFormSubmitter_applicantemailaddress1"]; 
    ApplicantMailNodeSelectors[1] = HttpContext.Current.Request.Form["MailFormSubmitter_applicantemailaddress2"]; 
    ApplicantMailNodeSelectors[2] = HttpContext.Current.Request.Form["MailFormSubmitter_applicantemailaddress3"]; 
} 

Answer 3

你的方法是无效的类型，这样你不能返回任何值。表达式return IsCheckPDfMailSubmit == null;尝试返回一个bool是不正确的，因为你会得到一个编译器错误。

你可以通过几种方式解决它，一种方法可能是改变你的条件来检查备用的情况。

public void ReadPostedData() 
{ 
    Sender = HttpContext.Current.Request.Form["MailFormSubmitter_sender"]; 
    Subject = HttpContext.Current.Request.Form["MailFormSubmitter_subject"];   
    Message = HttpContext.Current.Request.Form["Message"]; 
    PdfMessage = HttpContext.Current.Request.Form["PdfMessage"]; 

    string IsCheckPDfMailSubmit = HttpContext.Current.Request.Form["IsCheckedPDFMailForm"]; 
    if (IsCheckPDfMailSubmit != null && IsCheckPDfMailSubmit.Length > 0) 
    // A better option is to use string.IsNullOrEmpty: 
    // if (!string.IsNullOrEmpty(IsCheckPDfMailSubmit)) 
    { 

    IsCheckedPDFMailForm = IsCheckPDfMailSubmit.Equals("True", StringComparison.OrdinalIgnoreCase); 





    string v = HttpContext.Current.Request.Form["MailFormSubmitter_includeoverviewpdf"]; 
    IncludeOverviewPdf = v.Equals("true,false", StringComparison.Ordinal) ? true : false; 
    // http://forums.asp.net/t/1314753.aspx 

    ApplicantMailNodeSelectors[0] = HttpContext.Current.Request.Form["MailFormSubmitter_applicantemailaddress1"]; 
    ApplicantMailNodeSelectors[1] = HttpContext.Current.Request.Form["MailFormSubmitter_applicantemailaddress2"]; 
    ApplicantMailNodeSelectors[2] = HttpContext.Current.Request.Form["MailFormSubmitter_applicantemailaddress3"]; 
    } 
}