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));
    }
}

当我迁移到c#时，我错过了Visual Basic的With语句，所以它是这样的:

public static void With<T>(this T obj, Action<T> act) { act(obj); }

下面是如何在c#中使用它:

someVeryVeryLonggggVariableName.With(x => {
    x.Int = 123;
    x.Str = "Hello";
    x.Str2 = " World!";
});

节省了大量的输入!

将其与:

someVeryVeryLonggggVariableName.Int = 123;
someVeryVeryLonggggVariableName.Str = "Hello";
someVeryVeryLonggggVariableName.Str2 = " World!";

加入codeplex项目

一些DataSet/DataRow扩展，使使用db结果更简单

只需在DataRow上使用. field ("fieldname")，如果可以，它将强制转换它，可选的默认值可以包括在内。

还有DataSet上的. hasrows()，这样你就不需要检查表和行的存在。

例子:

using (DataSet ds = yourcall()) 
{
  if (ds.HasRows())
  {
     foreach (DataRow dr in ds.Tables[0].Rows)
     {
        int id = dr.Field<int>("ID");
        string name = dr.Field<string>("Name");
        string Action = dr.Field<string>("Action", "N/A");
     }
  }
}

代码:

using System;
using System.Data;

public static class DataSetExtensions
{
    public static T Field<T>(this DataRow row, string columnName, T defaultValue)
    {
        try
        {
            return row.Field<T>(columnName);
        }
        catch
        {
            return defaultValue;
        }
    }

    public static T Field<T>(this DataRow row, string columnName)
    {
        if (row[columnName] == null)
            throw new NullReferenceException(columnName + " does not exist in DataRow");

        string value = row[columnName].ToString();

        if (typeof(T) == "".GetType())
        {
            return (T)Convert.ChangeType(value, typeof(T));
        }
        else if (typeof(T) == 0.GetType())
        {
            return (T)Convert.ChangeType(int.Parse(value), typeof(T));
        }
        else if (typeof(T) == false.GetType())
        {
            return (T)Convert.ChangeType(bool.Parse(value), typeof(T));
        }
        else if (typeof(T) == DateTime.Now.GetType())
        {
            return (T)Convert.ChangeType(DateTime.Parse(value), typeof(T));
        }
        else if (typeof(T) == new byte().GetType())
        {
            return (T)Convert.ChangeType(byte.Parse(value), typeof(T));
        }
        else if (typeof(T) == new float().GetType())
        {
            return (T)Convert.ChangeType(float.Parse(value), typeof(T));
        }
        else
        {
            throw new ArgumentException(string.Format("Cannot cast '{0}' to '{1}'.", value, typeof(T).ToString()));
        }
    }

    public static bool HasRows(this DataSet dataSet) 
    {
        return (dataSet.Tables.Count > 0 && dataSet.Tables[0].Rows.Count > 0);
    }
}

用于winforms填充组合框:

List<MyObject> myObjects = new List<MyObject>() { 
    new MyObject() {Name = "a", Id = 0}, 
    new MyObject() {Name = "b", Id = 1}, 
    new MyObject() {Name = "c", Id = 2} }
comboBox.FillDataSource<MyObject>(myObjects, x => x.Name);

扩展方法:

/** <summary>Fills the System.Windows.Forms.ComboBox object DataSource with a 
 * list of T objects.</summary>
 * <param name="values">The list of T objects.</param>
 * <param name="displayedValue">A function to apply to each element to get the 
 * display value.</param>
 */
public static void FillDataSource<T>(this ComboBox comboBox, List<T> values,
    Func<T, String> displayedValue) {

    // Create dataTable
    DataTable data = new DataTable();
    data.Columns.Add("ValueMember", typeof(T));
    data.Columns.Add("DisplayMember");

    for (int i = 0; i < values.Count; i++) {
        // For each value/displayed value

        // Create new row with value & displayed value
        DataRow dr = data.NewRow();
        dr["ValueMember"] = values[i];
        dr["DisplayMember"] = displayedValue(values[i]) ?? "";
        // Add row to the dataTable
        data.Rows.Add(dr);
    }

    // Bind datasource to the comboBox
    comboBox.DataSource = data;
    comboBox.ValueMember = "ValueMember";
    comboBox.DisplayMember = "DisplayMember";
}

public static class DictionaryExtensions
{
    public static Nullable<TValue> GetValueOrNull<TKey, TValue>(this Dictionary<TKey, TValue> dictionary, TKey key)
        where TValue : struct
    {
        TValue result;
        if (dictionary.TryGetValue(key, out result))
            return result;
        else
            return null;
    }
}

免费使用，只需在代码中提到我的名字(Janko Röbisch)。

我相信以前有人这样做过，但我发现自己经常使用这种方法(和更简单的导数):

public static bool CompareEx(this string strA, string strB, CultureInfo culture, bool ignoreCase)
{
    return string.Compare(strA, strB, ignoreCase, culture) == 0;
}

您可以以多种方式编写它，但我喜欢它，因为它非常快速地统一了比较字符串的方法，同时节省了代码行数(或代码字符)。