C# Unreachable code detected

问题:

I'm getting a "Unreachable code detected" message in Visual Studio at the point i++ in my code below. Can you spot what I've done wrong?

try
{
    RegistryKey OurKey = Registry.CurrentUser;
    OurKey.CreateSubKey("Software\\Resources\\Shared");
    OurKey = OurKey.OpenSubKey("Software\\Resources\\Shared", true);
    for (int i = 0; i < cmbPaths.Items.Count; i++) //<---- problem with i
    {
        OurKey.SetValue("paths" + i, cmbPaths.Items[i]);
        break;
    }
}

回答1:

The problem is that this actually isn't a loop. You don't have any condition on the break so you could equivalently write something like

if(cmbPath.Items.Count > 0)
{
   OurKey.SetValue("paths" + 0, cmbPaths.Items[0]);
}

Alternatively you have to correct with something like

for (int i = 0; i < cmbPaths.Items.Count; i++) 
{
   OurKey.SetValue("paths" + i, cmbPaths.Items[i]);

   if(someConditionHolds)
      break;
}

回答2:

You're breaking out of the loop before the end of the first iteration.

回答3:

The problem is that because you break; in the loop with no chance of it doing anything else, the increment of i (i++) will never be reached.

回答4:

Although your problem is solved i need to tell you this, you can just using the CreateSubKey() method for your purpose. I think It's a better choice. :)

//Creates a new subkey or opens an existing subkey for write access.
var ourKey = Registry.CurrentUser.CreateSubKey("Software\\Resources\\Shared");

回答5:

You can also end up getting unreachable code if you use say for example Entity Framework, and you didn't add that reference to that project.

Say you have several projects like A Data Layer Project, a Domain Classes, then you create a console app for testing or whatever and you reference where your dbcontext is at, but if you don't use say nuget and add in EF, you will get code unreachable when trying to write a loop etc...