c# - 如果字符串为空则跳行

Question

如果字符串为空，我想跳过一行。

我这样试:

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"];
}

是关于这一行的:

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

如果为空，则不执行此行:

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

我这样试:

return IsCheckPDfMailSubmit == null;

但随后出现以下错误:

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

那么如何跳过呢？

Answer 1

如果你想根据 if 语句中的条件退出函数，你只需使用 return; 当方法有 void 作为返回类型:

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

或者，您可以反转条件并将其余代码放在 if 语句中，而不是在函数中间退出:

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

如果您只是想跳过下面这行而继续使用方法中的其余代码，请反转条件并将该行放在 if 语句中:

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