使用 If Then Else If 根据首字母选择姓氏，然后显示 MessageBox [英] Using If Then Else If to select Last Name based on First Letter then Display a MessageBox

问题描述

我正在学习介绍.这学期编程，我们用的是VB.我被我的一部分编码难住了.当我单击处理"按钮时，我需要一条消息来显示您在第 3 行.您的密码是 *."

I'm taking Intro. to Programming this semester and we are using VB. I'm stumped on a part of my coding. When I click the "process" button, I need a Message to display "You are in line 3. Your pin number is *."

PIN 码必须由名字的第一个字母、中间名的第一个字母、姓氏的第一个字母和 ID 的前 2 位数字组成.

The pin number must be made of first letter of first name, first letter of middle name, first letter of last name, and first 2 digits of id.

我就是这样开始的，但我知道我要放弃一些东西.条目不应区分大小写.当我只输入一个字母 ex 时.姓氏中的a"它给了我结果例如.第 1 行"，但是当我输入一个完整的姓氏时.艾伦"它什么也没给我.

This is how I've started, but I know I'm leaving something off. Entries should not be case sensitive. When I type just a letter ex. "a" in last name it gives me the result ex. "line 1", but when I type a full last name ex. "allen" it gives me nothing.

'使用 if then 判断哪一行消息

'Use if then to determine which line message

    If strLastName.Substring(0) = "a-c" Then
        strMessage = "line 1."
    ElseIf strLastName.Substring(0) = "g-l" Then
        strMessage = "line 2."
    ElseIf strLastName.Substring(0) = "m-q" Then
        strMessage = "line 3."
    ElseIf strLastName.Substring(0) = " r-v" Then
        strMessage = "line 4."
    ElseIf strLastName.Substring(0) = "w-z" Then
        strMessage = "line 5."


    End If

    MessageBox.Show("You are in " & strMessage & " "Your pin number is " & )
End Sub

推荐答案

If 不是这样工作的.strLastName.Substring(0) = "a-c" 将测试第一个字符是否等于a-c"，而这永远不可能.甚至a"都不应该工作.这可能不适用于外国字符集，但它是您尝试执行的操作的紧凑形式:

If doesnt work like that. strLastName.Substring(0) = "a-c" will be testing if the first character equals "a-c" which it never can be. Not even "a" should work. This likely wont work on foreign character sets, but is a compact form of what you are trying to do:

Select Case strLastName.ToUpper.Substring(0, 1)
    Case "A" ,"B", "C"            ' test range
       strMsg = "line 1"

    Case "D" to "G"            ' forgot these
       strMsg = "line 2"

使用范围作为问题中的代码似乎需要，可以工作，但指定每个字符更好.或者，您可以测试第一个字符是否在表示范围的字符串中:

Using a range as the code in the questions seems to want, can work but specifying each character is better. Alternatively, you could test if the first char is in a string representing a range:

' read the char array of the string for the first letter
Dim ch As String = strLastName(0)

If "ABC".Contains(ch.ToUpper) Then

ElseIf "DEFG".Contains(ch.ToUpper) Then
'...

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