C＃声明变量进入if语句 [英] C# declare variable into if statement

问题描述

我想要做这样的事情使用C＃：

i want to do something like this using C# :

if (i == 0)
{
 button a = new button();
}
else
{
 TextBlock a = new TextBlock();
}
mainpage.children.add(a);

但我得到一个错误，

But i get an error that

错误1名'一个'不在当前情况下存在

Error 1 The name 'a' does not exist in the current context

任何想法？

感谢你在前进！

推荐答案

您需要一个共同的基类，这两个按钮和文本块从派生，它需要外部的如果语句，如果它是在如果来访问已完成。 控制也许

You need a common base class that both button and Textblock derive from, and it needs to be declared outside of the if statement if it's to be accessed after the if is complete. Control maybe?

Control a;
if (i == 0)
{
 a = new button();
}
else
{
 a = new TextBlock();
}
mainpage.children.add(a);

不知道你用什么具体的控制工具包（WPF也许？）我不能再提醒。但我会看签名添加来得到一个线索 - 有什么声明

Not knowing what specific control toolkit you're using (WPF maybe?) I can't advise further. But I'd look at the signature for Add to get a clue - what's the parameter declared as?

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