为什么我的方法不起作用？ [英] Why my method isnt working?

问题描述

public void GetVal(string msg, double value)
        {
            if (comPort.IsOpen == true)
            {
                comPort.WriteLine(msg);
            }
            Thread.Sleep(200);
            string buff = comPort.ReadLine();
            Thread.Sleep(200);
            string numberPart = buff.Substring(buff.LastIndexOf(' ')).Trim();
            value = double.Parse(numberPart);
            
        }

这是我的方法（），但事情是我称之为例子：GetVal（" VA VV_IN"，vv_in）

this is my Method(), but the thing is when i call it example: GetVal("VA VV_IN", vv_in)

我在变量vv_in中得到的值是0，当我使方法没有"double value"时而我写"vv_in = double.Parse（numberPart）我在vv_in中得到的值是想要的值...

the value i get in my variable vv_in is 0, when i make the method without "double value" and instead i write "vv_in = double.Parse(numberPart) the value i get in the vv_in is the wanted value...

推荐答案

看起来你真的想要从方法中返回值？

It looks like you actually want to return the value from the method?

在这种情况下你可以......通过将方法声明为返回double并分配结果来返回它在调用它时进入你的vv_in变量：

In which case you could just...return it by declaring the method as returning a double and assigning the result into your vv_in variable when you call it:

public double GetVal(string msg)
        {
            if (comPort.IsOpen == true)
            {
                comPort.WriteLine(msg);
            }
            Thread.Sleep(200);
            string buff = comPort.ReadLine();
            Thread.Sleep(200);
            string numberPart = buff.Substring(buff.LastIndexOf(' ')).Trim();
            return double.Parse(numberPart);
            
        }

然后调用它：

vv_in = GetVal("VA VV_IN")

或者你可以将value参数声明为'ref'或'out'参数，但是当你只是将值作为方法结果返回时，这似乎是不必要的。

Alternately you could declare the value argument as a 'ref' or 'out' parameter, but this just seems unnecessary when you can simply return the value as the method result.

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