GetMemberName允许在编译时安全的情况下获取带有成员名称的字符串。

public static string GetMemberName<T, TResult>(
    this T anyObject, 
    Expression<Func<T, TResult>> expression)
{
    return ((MemberExpression)expression.Body).Member.Name;
}

用法:

"blah".GetMemberName(x => x.Length); // returns "Length"

如果你没有实例，它会和一个非扩展静态方法一起出现:

public static string GetMemberName<T, TReturn>(
    Expression<Func<T, TReturn>> expression)
    where T : class
{
    return ((MemberExpression)expression.Body).Member.Name;
}

当然，这个电话看起来并不漂亮:

ReflectionUtility.GetMemberName((string) s => s.Length); // returns "Length"

如果你愿意，可以用Codeplex。

将double类型转换为使用指定区域性格式化的字符串:

public static class ExtensionMethods 
{
  public static string ToCurrency(this double value, string cultureName)
  {
    CultureInfo currentCulture = new CultureInfo(cultureName);
    return (string.Format(currentCulture, "{0:C}", value));
  }
}

例子:

double test = 154.20;
string testString = test.ToCurrency("en-US"); // $154.20

轻松序列化对象为XML:

public static string ToXml<T>(this T obj) where T : class
{
    XmlSerializer s = new XmlSerializer(obj.GetType());
    using (StringWriter writer = new StringWriter())
    {
        s.Serialize(writer, obj);
        return writer.ToString();
    }
}

"<root><child>foo</child</root>".ToXml<MyCustomType>();

ThrowIfArgumentIsNull是做空检查的好方法，我们都应该这样做。

public static class Extensions
{
    public static void ThrowIfArgumentIsNull<T>(this T obj, string parameterName) where T : class
    {
        if (obj == null) throw new ArgumentNullException(parameterName + " not allowed to be null");
    }
}

下面是使用它的方法，它适用于您的命名空间中的所有类或任何您使用该命名空间的地方。

internal class Test
{
    public Test(string input1)
    {
        input1.ThrowIfArgumentIsNull("input1");
    }
}

在CodePlex项目上使用这段代码是可以的。

通过操作系统文件系统信息比较文件/目录。这对于比较共享和本地文件非常有用。

用法:

DirectoryInfo dir = new DirectoryInfo(@"C:\test\myShareDir");
Console.WriteLine(dir.IsSameFileAs(@"\\myMachineName\myShareDir"));

FileInfo file = new FileInfo(@"C:\test\myShareDir\file.txt");
Console.WriteLine(file.IsSameFileAs(@"\\myMachineName\myShareDir\file.txt"));

代码:

public static class FileExtensions
{
    struct BY_HANDLE_FILE_INFORMATION
    {
        public uint FileAttributes;
        public System.Runtime.InteropServices.ComTypes.FILETIME CreationTime;
        public System.Runtime.InteropServices.ComTypes.FILETIME LastAccessTime;
        public System.Runtime.InteropServices.ComTypes.FILETIME LastWriteTime;
        public uint VolumeSerialNumber;
        public uint FileSizeHigh;
        public uint FileSizeLow;
        public uint NumberOfLinks;
        public uint FileIndexHigh;
        public uint FileIndexLow;
    }

    //
    // CreateFile constants
    //
    const uint FILE_SHARE_READ = 0x00000001;
    const uint OPEN_EXISTING = 3;
    const uint GENERIC_READ = (0x80000000);
    const uint FILE_FLAG_BACKUP_SEMANTICS = 0x02000000;


    [DllImport("kernel32.dll", SetLastError = true)]
    static extern IntPtr CreateFile(
        string lpFileName,
        uint dwDesiredAccess,
        uint dwShareMode,
        IntPtr lpSecurityAttributes,
        uint dwCreationDisposition,
        uint dwFlagsAndAttributes,
        IntPtr hTemplateFile);

    [DllImport("kernel32.dll", SetLastError = true)]
    static extern bool GetFileInformationByHandle(IntPtr hFile, out BY_HANDLE_FILE_INFORMATION lpFileInformation);

    public static bool IsSameFileAs(this FileSystemInfo file, string path)
    {
        BY_HANDLE_FILE_INFORMATION fileInfo1, fileInfo2;
        IntPtr ptr1 = CreateFile(file.FullName, GENERIC_READ, FILE_SHARE_READ, IntPtr.Zero, OPEN_EXISTING, FILE_FLAG_BACKUP_SEMANTICS, IntPtr.Zero);
        if ((int)ptr1 == -1)
        {
            System.ComponentModel.Win32Exception e = new System.ComponentModel.Win32Exception(Marshal.GetLastWin32Error());
            throw e;
        }
        IntPtr ptr2 = CreateFile(path, GENERIC_READ, FILE_SHARE_READ, IntPtr.Zero, OPEN_EXISTING, FILE_FLAG_BACKUP_SEMANTICS, IntPtr.Zero);
        if ((int)ptr2 == -1)
        {
            System.ComponentModel.Win32Exception e = new System.ComponentModel.Win32Exception(Marshal.GetLastWin32Error());
            throw e;
        }
        GetFileInformationByHandle(ptr1, out fileInfo1);
        GetFileInformationByHandle(ptr2, out fileInfo2);

        return ((fileInfo1.FileIndexHigh == fileInfo2.FileIndexHigh) &&
            (fileInfo1.FileIndexLow == fileInfo2.FileIndexLow));
    }
}

这是ThrowIfNull的另一个实现:

[ThreadStatic]
private static string lastMethodName = null;

[ThreadStatic]
private static int lastParamIndex = 0;

[MethodImpl(MethodImplOptions.NoInlining)]
public static void ThrowIfNull<T>(this T parameter)
{
    var currentStackFrame = new StackFrame(1);
    var props = currentStackFrame.GetMethod().GetParameters();

    if (!String.IsNullOrEmpty(lastMethodName)) {
        if (currentStackFrame.GetMethod().Name != lastMethodName) {
            lastParamIndex = 0;
        } else if (lastParamIndex >= props.Length - 1) {
            lastParamIndex = 0;
        } else {
            lastParamIndex++;
        }
    } else {
        lastParamIndex = 0;
    }

    if (!typeof(T).IsValueType) {
        for (int i = lastParamIndex; i &lt; props.Length; i++) {
            if (props[i].ParameterType.IsValueType) {
                lastParamIndex++;
            } else {
                break;
            }
        }
    }

    if (parameter == null) {
        string paramName = props[lastParamIndex].Name;
        throw new ArgumentNullException(paramName);
    }

    lastMethodName = currentStackFrame.GetMethod().Name;
}

它不像其他实现那样高效，但有更干净的用法:

public void Foo()
{
    Bar(1, 2, "Hello", "World"); //no exception
    Bar(1, 2, "Hello", null); //exception
    Bar(1, 2, null, "World"); //exception
}

public void Bar(int x, int y, string someString1, string someString2)
{
    //will also work with comments removed
    //x.ThrowIfNull();
    //y.ThrowIfNull();
    someString1.ThrowIfNull();
    someString2.ThrowIfNull();

    //Do something incredibly useful here!
}

改变参数为int?也会起作用。

那