C# 在声明之前不能使用局部变量
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Cannot use local variable before it is declared
提问by user1084113
I am trying to create a function but I'm getting an error message.
我正在尝试创建一个函数，但收到一条错误消息。
public int[] genericSearch(int searchWidth, int startingRadius, int width, int height, Bitmap bitmap)
{
//Generic function for finding the best path from a certain range
if (startingRadius == -1)
startingRadius = bitmap.Height() / 2;
Cannot use local variable 'startingRadius' before it is declared.
不能在声明之前使用局部变量 'startingRadius'。
The same problem occurs for the bitmap variable as well. Normally in c++ this type of declaration would work; however, I am unsure why it is not working here.
同样的问题也发生在位图变量上。通常在 C++ 中，这种类型的声明会起作用；但是，我不确定为什么它在这里不起作用。
回答by Kevin
You are missing a closing brace for your method but otherwise this code can compile on my machine... (changed Height to a property as well)
您的方法缺少右括号，否则此代码可以在我的机器上编译...（也将 Height 更改为属性）
public int[] genericSearch(int searchWidth, int startingRadius, int width, int height,Bitmap bitmap)
{
//Generic function for finding the best path from a certain range
if (startingRadius == -1)
startingRadius = bitmap.Height / 2;
}
回答by Stephen
It sounds like you have a misplaced }or misspelled variable names. I can't really tell without seeing the full code.
听起来你有一个错位}或拼写错误的变量名。如果没有看到完整的代码，我真的无法判断。
The error message is basically telling you that you have a local variable that you are trying to use which has not been declared. Which suggests that the if (startingRadius == 1)code is actually inside a different method than the method you have declared.
该错误消息基本上是在告诉您，您有一个您正在尝试使用的未声明的局部变量。这表明if (startingRadius == 1)代码实际上位于与您声明的方法不同的方法中。
回答by gunwin
In visual studio. Sometimes when you declare a variable again (a second time). It will give this error. For example, this will sometimes throw the exception you mentioned:
在视觉工作室。有时当你再次声明一个变量时（第二次）。它会给出这个错误。例如，这有时会抛出您提到的异常：
1. int startingRadius = 0;
2. startingRadius = 5; <-- Exception thrown here.
3.
4. int startingRadius = 0;
Obviously this is incorrect anyway. So removing the second declaration (on line 4) will solve the problem.
显然，无论如何这是不正确的。因此删除第二个声明（在第 4 行）将解决问题。
Note: The exception you would ordinarily expect would be A local variable named 'startingRadius' is already defined in this scope. But for some reason, the exception you mentioned is shown sometimes.
注意：您通常期望的例外是A local variable named 'startingRadius' is already defined in this scope. 但是由于某种原因，有时会显示您提到的异常。
