如何从一个方法返回多个变量？

Question

This method returns only the process filename:

public static string GetProcessInfo(IntPtr hwnd)
{
    uint pid = 0;
    GetWindowThreadProcessId(hwnd, out pid);
    Process proc = Process.GetProcessById((int)pid);
    return proc.MainModule.FileName.ToString();
}

But I want to return also the process name:

proc.ProcessName;

Answer 1

I believe you have four options (in preference order)

• Return proc.MainModule directly and extract necessary information from caller.

public static ProcessModule GetProcessInfo(IntPtr hwnd)
{
    uint pid = 0;
    GetWindowThreadProcessId(hwnd, out pid);
    Process proc = Process.GetProcessById((int)pid);
    return proc.MainModule;
}

• Create a class containing both values and return that

public class ProcessInformation
{
    public string FileName;
    public string ProcessName;
}

public static ProcessInformation GetProcessInfo(IntPtr hwnd)
{
    uint pid = 0;
    GetWindowThreadProcessId(hwnd, out pid);
    Process proc = Process.GetProcessById((int)pid);
    var pi = new ProcessInformation 
    {  
        proc.MainModule.FileName,
        proc.MainModule.ProcessName
    }
    return pi;
}

• Return a tuple from method Tuple<string, string>

public static Tuple<string, string> GetProcessInfo(IntPtr hwnd)
{
    uint pid = 0;
    GetWindowThreadProcessId(hwnd, out pid);
    Process proc = Process.GetProcessById((int)pid);
    return return Tuple.Create(proc.MainModule.FileName,proc.MainModule.ProcessName);
}

• Create 2 out parameters on your method (I never seen two out parameters implemented and I discourage this since definitively smells, but it's an option C# provides)

string GetProcessInfo(IntPtr hwnd, out fileName, out processName)

Answer 2

You can create and return an object describing your result:

public class ProcessInfo
{
    public string ProcessName { get; set; }
    public string FileName { get; set; }
}

public ProcessInfo GetProcessInfo(IntPtr hwnd)
{
    uint pid = 0;
    GetWindowThreadProcessId(hwnd, out pid);
    Process proc = Process.GetProcessById((int)pid);

    return new ProcessInfo 
    {
        FileName = proc.MainModule.FileName.ToString(),
        ProcessName = proc.ProcessName
    }
 }

Or (I personally like this less), a Tuple<string, string> :

public Tuple<string, string> GetProcessInfo(IntPtr hwnd)
{
    uint pid = 0;
    GetWindowThreadProcessId(hwnd, out pid);
    Process proc = Process.GetProcessById((int)pid);

    return Tuple.Create(proc.MainModule.FileName.ToString(),
                        proc.ProcessName);
}

Answer 3

Since both are string , how about return a Tuple<string, string> instead?

public static Tuple<string, string> GetProcessInfo(IntPtr hwnd)
{
    uint pid = 0;
    GetWindowThreadProcessId(hwnd, out pid);
    Process proc = Process.GetProcessById((int)pid);
    Tuple<string, string> t = new Tuple<string, string>
    (
         proc.MainModule.FileName,
         proc.ProcessName
    );
    return t;
}

Answer 4

Last option would be using out-params:

public voidstring GetProcessInfo(IntPtr hwnd, out string fileName, out string processName{
    uint pid = 0;
    GetWindowThreadProcessId(hwnd, out pid);
    Process proc = Process.GetProcessById((int)pid);
    fileName = proc.MainModule.FileName.ToString();
    processName = proc.ProcessName;
}

Answer 5

You could change the return type to Process :

    public static Process GetProcessInfo(IntPtr hwnd)
    {
        uint pid = 0;
        GetWindowThreadProcessId(hwnd, out pid);
        return Process.GetProcessById((int)pid);
     }

and then get the data you need from the returned object:

var proc = GetProcessInfo(hwnd);
var processName = proc.ProcessName;
var moduleFileName = proc.MainModule.FileName.ToString();