每当我调用我的子过程时出现错误“表达式不产生值”

Question

首先，我会说我是新来的，所以我可能无法正确解释我的问题。我使用 VB.Net Windows 窗体应用程序。在这个项目中，我必须从另一个类调用sub 过程，以便在单击按钮时显示报告。 sub 不返回我知道的值，而且我已经习惯了，每当我有 sub 时，我都会在 sub 中显示该值，但我不能在另一个中写入文本框的名称班级 。这些是我的代码，希望您能从中理解我的意思。

Public Class Form1
    Dim aobj As New Allowance
    Dim nam As String
    Dim ID, year, allowance, total As Double

    Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
        allowance = txtamount.Text
        total = aobj.calculatetotal(allowance)
        txtcalculate.ForeColor = Color.Red
        txtcalculate.Text = FormatNumber(total)
    End Sub

    Private Sub Button2_Click(sender As System.Object, e As System.EventArgs) Handles Button2.Click
        ID = txtid.Text
        year = txtyear.Text
        nam = txtname.Text
        txtreport.ForeColor = Color.Blue
        txtreport.Text = aobj.displayreport(nam, ID, year, total)
    End Sub
End Class

Class Allowance

    Function calculatetotal(ByVal a As Double) As Double
        Return (12 * 5 * a)
    End Function

    Sub displayreport(ByVal nam As String, ByVal id As Double, ByVal y As Double, ByVal tot As Double)

         (" The Student " & nam & " with ID: " & id & " will receivce a total allowance of " & tot & " for five years of study in YUC")
    End Sub

End Class 

Answer 1

如果要将字符串分配给 txtreport.Text，则需要将 displayreport 更改为函数并返回该字符串。尝试将其更改为：

Public Function displayreport(ByVal nam As String, ByVal id As Double, ByVal tot As Double) As String
    Return " The Student " & nam & " with ID: " & id & " will receivce a total allowance of " & tot & " for five years of study in YUC"
End Function

我还删除了“y as double”，因为它没有被使用