如果 VB.NET (IIf) 的条件不等于 C# (?:) [英] If Condition of VB.NET (IIf) is not equal by C# (?:)

问题描述

VB 中的IIf 函数.NET:

IIf(condition As Boolean, TruePart As Object, FalsePart As Object) As Object

完全不等于 C# 条件运算符 (?:):

condition ? first_expression : second_expression;

当我将一些代码从 c# 转换为 vb.net 时，我知道转换后的代码无法正常工作，因为在 vb.net 中，如果条件在检查条件之前评估了真假部分！

When I convert some codes from c# to vb.net, I understand that converted codes not work correctly because in vb.net if conditional are evaluated both of the true and false parts before the condition is checked!

例如，C#:

public int Divide(int number, int divisor)
{
    var result = (divisor == 0) 
                 ? AlertDivideByZeroException() 
                 : number / divisor;

    return result;
}

VB.NET:

Public Function Divide(number As Int32, divisor As Int32) As Int32

     Dim result = IIf(divisor = 0, _
                  AlertDivideByZeroException(), _
                  number / divisor)

     Return result

End Function

现在，我的 c# 代码成功执行，但每次 divisor 不等于零时，vb.net 代码都会运行 AlertDivideByZeroException() 和 number/除数.

Now, my c# codes executed successfully but vb.net codes every times that divisor is not equal by zero, runs both of AlertDivideByZeroException() and number / divisor.

为什么会这样?

和

如何以及用什么替换 VB.net 中的 c# if 条件运算符 (?:)?

推荐答案

在 Visual Basic 中，相等运算符是 =，而不是 ==.您只需将 divisor == 0 更改为 divisor = 0.

In Visual Basic, the equality operator is =, not ==. All you need to change is divisor == 0 to divisor = 0.

另外，正如马克所说，你应该使用 If 而不是 IIf.来自 If 的文档:使用三个参数调用的 If 运算符的工作方式与 IIf 函数类似，只是它使用短路求值. 由于 C# 使用短路求值，您将希望在 VB 中使用 If 来实现相同的功能.

Also, as Mark said, you should use If instead of IIf. From the documentation on If: An If operator that is called with three arguments works like an IIf function except that it uses short-circuit evaluation. Since C# uses short-circuit evaluation, you will want to use If for the same functionality in VB.

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