How can Path.Combine be used with more than two arguments?

问题

I'm surprised there's not an overload that can take a string array. Anyway, what is the best way to avoid nesting calls to Path.Combine?

pathValue = Path.Combine(path1, Path.Combine(path2, Path.Combine(path3, path4)))

This seems inefficient since it results in four new strings being created just to get one.

回答1:

The efficiency side of things isn't the problem IMO - it's the usability side of things. Personally I think there ought to be an overload of:

Combine(string first, string second, string third, params string[] others)

You need to have at least three to prevent it from clashing with the existing two-parameter version if you just write Path.Combine("foo", "bar") but it would certainly help to make code clearer. Why not open a feature request on Connect?

Of course, you can implement this yourself (and in another class the number of parameters doesn't matter so much):

public static string CombinePaths(string first, params string[] others)
{
    // Put error checking in here :)
    string path = first;
    foreach (string section in others)
    {
        path = Path.Combine(path, section);
    }
    return path;
}

回答2:

If you already have an array or an IEnumerable<T> then you could do this in one line...

// I'm assuming that you've got an array or IEnumerable<T> from somewhere
var paths = new string[] { path1, path2, path3, path4, path5, path6 };

string result = paths.Aggregate(Path.Combine);

If not, then write your own extension method to string...

public static class PathExtension
{
    public static string CombinePathWith(this string path1, string path2)
    {
        return Path.Combine(path1, path2);
    }
}

... that would allow you to chain these like this...

string result = path1.CombinePathWith(path2)
                     .CombinePathWith(path3)
                     .CombinePathWith(path4)
                     .CombinePathWith(path5)
                     .CombinePathWith(path6);

回答3:

It's pretty straightforward to implement it yourself:

public string Combine(params string[] paths)
{
    char[] pathSeparators = new char[] 
        { Path.AltDirectorySeparatorChar, Path.DirectorySeparatorChar, Path.VolumeSeparatorChar };

    if(paths == null) throw new ArgumentNullException("paths");
    if(paths.Length == 1) return paths[0];

    StringBuilder pathBuilder = new StringBuilder();

    foreach(string path in paths)
    {
        if(Path.IsPathRooted(path))
            pathBuilder = new StringBuilder(path);
        else
        {
            char last = pathBuilder.Length > 0 ?
                pathBuilder[pathBuilder.Length - 1] :
                path[path.Length - 1];

            if(Array.IndexOf(pathSeparators, last) == -1)
                pathBuilder.Append(Path.DirectorySeparatorChar);

            pathBuilder.Append(path);
        } // else
    } // foreach

    return pathBuilder.ToString();
}

[Test()]
public void CombinePaths()
{
    string result = Combine(@"C:\Program Files\", @"Microsoft.NET", @"ADOMD.NET\", "90", "msadomdx.dll");
    Assert.AreEqual(@"C:\Program Files\Microsoft.NET\ADOMD.NET\90\msadomdx.dll", result);
}

来源：https://stackoverflow.com/questions/760612/how-can-path-combine-be-used-with-more-than-two-arguments

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concatenation