我的輸出發生了什麼？ （我是否正確使用「沒什麼」？）

Question

我有一個網頁表單，它可能會或可能不會在提交時產生空白答案。爲了彌補這一點，我寫了一個for循環來設置每個變量爲空的字符串「（空白）。但是for循環不返回任何內容。 我的輸出發生了什麼？我是否正確使用」Is Nothing「？

Imports System.Data.OleDb 
Imports System.Net.Mail 
Imports System.Text 

Partial Class acen_EarlyIntervention 
    Inherits System.Web.UI.Page 

    Protected Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click 
     'Insert Form Values into an array 

     Dim strDate As String = "Date: " & Dates.Text 
     Dim strStudent As String = "Student: " & Student.Text 
     Dim strUin As String = "UIN: " & UIN.Text 
     Dim strSContact As String = "Student Contact: " & SContact.Text() 

     Dim strCourse As String = "Course: " & Course.Text 
     Dim strFaculty As String = "Refering Facilty: " & Refer.Text 
     Dim strFContact As String = "Faculty Contact: " & FContact.Text 
     Dim strReason As String = "Reasons:" & Reason.Text 

     Dim strPContact As String = "Previous Contact: " & Before.Text 
     Dim strMContact As String = "Mthod of Contact: " & DropDownList1.Text 
     Dim strOMC As String = "Other Method of Contact: " & TextBox8.Text 
     Dim strComment As String = "Additional Comments: " & TextBox9.Text 
     'Creating email string 

     Dim sBodyBuilder As New StringBuilder 
     Dim values As String() = {strDate, strStudent, strUin, strSContact, strCourse, strFaculty, strFContact, strReason, strPContact, strMContact, strOMC, strComment} 
     For Each item In values 
      If item Is Nothing Then 
       item = "(blank)" 
       sBodyBuilder.AppendLine(item) 
      End If 
     Next item 

     Dim body As String = sBodyBuilder.ToString 

Answer 1

使用是沒有什麼檢查，看看是否該字符串引用未設置。這是同在C＃中的空檢查，你可能想要做的是檢查它是否是一個空字符串什麼。嘗試使用String.IsNullOrEmpty

If String.IsNullOrEmpty(item) Then