代码的简要信息如下。该代码采用一堆字符串并将它们连接起来,如下所示,中间有一个 if 语句来决定是否连接其中一个。问题是If(Evaluation, "", "")
抱怨说它不能为空或必须是资源。当评估只是检查一个对象以确保它 IsNot Nothing 并且对象中的一个属性被检查为时,我该如何解决这个问题如下:
Dim R as string = stringA & " * sample text" & _
stringB & " * sample text2" & _
stringC & " * sameple text3" & _
If(ApplyValue IsNot Nothing AndAlso ApplyValue.CheckedBox Then ,StringD & " * sample text4" & _
, NOTHING)
stringE & " * sample text5"
VS 抱怨 applyValue。有任何想法吗?
应该注意的是,我已经尝试了以下方法,看看它是否会起作用,而 VS 拒绝了它:
Dim y As Double
Dim d As String = "string1 *" & _
"string2 *" & _
If(y IsNot Nothing, " * sample text4", "") & _
"string4 *"
这就是它标记 y 的内容:
'IsNot' requires operands that have reference types, but this operand has the value type 'Double'. C:\Users\Skindeep\AppData\Local\Temporary Projects\WindowsApplication1\Form1.vb 13 16 WindowsApplication1