如何在方法中将接口对象分配给动态对象？答案

【问题标题】：How can i assign an interface object to dynamic object in a method?如何在方法中将接口对象分配给动态对象？
【发布时间】：2018-12-26 10:29:27
【问题描述】：

我正在尝试创建一个函数，用于将接口对象分配给我在结构中轻松创建的动态对象。这是我的结构：

public struct PSU
{
    public CheckBox CallHostessButton0, CallHostessButton1,
        ReadLightButton0, ReadLightButton1, ReadLightButton2, ReadLightButton3;
    public PictureBox BeltLight, SmokeLight;
}

这是我的功能：

public void AssignObjectsToPSU(UniversalVariables.PSU psu, CheckBox 
CallHostessBtn0, EventHandler HBtn0CheckedChanged, CheckBox 
CallHostessBtn1, EventHandler HBtn1CheckedChanged)
{
// and i'm trying to do this in my function:
...
psu.CallHostessButton0 = CallHostessBtn0;
psu.CallHostessButton0.CheckedChanged += new EventHandler(HBtn0CheckedChanged); 
...
}

程序运行顺利，但是当我尝试在 CheckedChanged 事件中执行此操作时：

if (TestPSU.CallHostessButton0.Checked)
{
    TestPSU.CallHostessButton0.BackgroundImage = Properties.Resources.lamp_on;
}
else
{
    TestPSU.CallHostessButton0.BackgroundImage = Properties.Resources.lamp_off;
}

程序给出一个错误：

Exception thrown: 'System.NullReferenceException' in IOS_Interface.exe
TestPSU.**CallHostessButton0** was null.

它怎么可能是空的？我在我的 AssignObjectsToPSU 方法上分配这个？

【问题讨论】：

标签： c# object methods dynamic

【解决方案1】：

我找到了一个解决方案，只需将结构类型更改为类就可以了。

我改变了这些：

public struct PSU
{
     public CheckBox CallHostessButton0, CallHostessButton1,
     ReadLightButton0, ReadLightButton1, ReadLightButton2, ReadLightButton3;
     public PictureBox BeltLight, SmokeLight;
 }

 public void AssignObjectsToPSU(UniversalVariables.PSU psu, CheckBox 
 CallHostessBtn0, EventHandler HBtn0CheckedChanged, CheckBox 
 CallHostessBtn1, EventHandler HBtn1CheckedChanged)
 {
 // and i'm trying to do this in my function:
 ...
 psu.CallHostessButton0 = CallHostessBtn0;
 psu.CallHostessButton0.CheckedChanged += new EventHandler(HBtn0CheckedChanged); 
 ...
 }

到这里：

//UniversalVariables.cs
public class PSU
{
    public CheckBox CallHostessButton0, CallHostessButton1,
        ReadLightButton0, ReadLightButton1, ReadLightButton2, ReadLightButton3;
    public PictureBox BeltLight, SmokeLight;

    public PSU(CheckBox CallHostBtn0, CheckBox CallHostBtn1, CheckBox ReadLightBtn0, CheckBox ReadLightBtn1,
        PictureBox BeltLght, PictureBox SmokeLght, [Optional] CheckBox ReadLightBtn2, [Optional] CheckBox ReadLightBtn3)
    {
        Log("[Info] Assigning objects to PSU unit...");
        CallHostessButton0 = CallHostBtn0;
        CallHostessButton1 = CallHostBtn1;
        ReadLightButton0 = ReadLightBtn0;
        ReadLightButton1 = ReadLightBtn1;

        if (CallHostessButton0 == null || CallHostessButton1 == null || ReadLightButton1 == null || ReadLightButton0 == null)
        {
            LogReport("[Failed]");
        }

        else { LogReport("[OK]"); }

        if (ReadLightBtn2 != null)
        {
            Log(String.Format("[Info] Extra {0} detected...", nameof(ReadLightBtn2)));
            this.ReadLightButton2 = ReadLightBtn2;
            LogReport("[OK]");

            if(ReadLightBtn3 != null)
            {
                Log(String.Format("[Info] Extra {0} detected...", nameof(ReadLightBtn3)));
                this.ReadLightButton3 = ReadLightBtn3;
                LogReport("[OK]");
            }
        }

        this.BeltLight = BeltLght; this.SmokeLight = SmokeLght;
    }

当你想定义新的 PSU 时，你只需要在你的表单代码中这样做：

 // Interface.cs
 UniversalVariables.PSU[] TestPSU = new UniversalVariables.PSU()cb_CallHost0, cb_CallHost1, cb_ReadLight0, cb_ReadLight1, pb_BeltLghtTest, pb_SmkLghtTest);

或者您需要一组 PSU（或者您的项目需要类似的东西）：

 //Interface.cs
 UniversalVariables.PSU[] TestPSU = new UniversalVariables.PSU[12];
 TestPSU[<indexOfYourPSU>] = new UniversalVariables.PSU(cb_CallHost0, cb_CallHost1, cb_ReadLight0, cb_ReadLight1, pb_BeltLghtTest, pb_SmkLghtTest);

它成功了 :) 我希望这次经历可以帮助到某人。祝你有美好的一天...

【讨论】：