另一个对我有用的是:

/// <summary>
/// Converts any type in to an Int32
/// </summary>
/// <typeparam name="T">Any Object</typeparam>
/// <param name="value">Value to convert</param>
/// <returns>The integer, 0 if unsuccessful</returns>
public static int ToInt32<T>(this T value)
{
  int result;
  if (int.TryParse(value.ToString(), out result))
  {
    return result;
  }
  return 0;
}

/// <summary>
/// Converts any type in to an Int32 but if null then returns the default
/// </summary>
/// <param name="value">Value to convert</param>
/// <typeparam name="T">Any Object</typeparam>
/// <param name="defaultValue">Default to use</param>
/// <returns>The defaultValue if unsuccessful</returns>
public static int ToInt32<T>(this T value, int defaultValue)
{
  int result;
  if (int.TryParse(value.ToString(), out result))
  {
    return result;
  }
  return defaultValue;
}

例子:

int number = "123".ToInt32();

or:

int badNumber = "a".ToInt32(100); // Returns 100 since a is nan

日期时间扩展

例子:

DateTime firstDayOfMonth = DateTime.Now.First();
DateTime lastdayOfMonth = DateTime.Now.Last();
DateTime lastFridayInMonth = DateTime.Now.Last(DayOfWeek.Friday);
DateTime nextFriday = DateTime.Now.Next(DayOfWeek.Friday);
DateTime lunchTime = DateTime.Now.SetTime(11, 30);
DateTime noonOnFriday = DateTime.Now.Next(DayOfWeek.Friday).Noon();
DateTime secondMondayOfMonth = DateTime.Now.First(DayOfWeek.Monday).Next(DayOfWeek.Monday).Midnight();

这是我经常使用的控件调用扩展;

public static class InvokeExtensions
{
    public static void InvokeHandler(this Control control, MethodInvoker del) // Sync. control-invoke extension.
    {
        if (control.InvokeRequired)
        {
            control.Invoke(del);
            return; 
        }
        del(); // run the actual code.
    }

    public static void AsyncInvokeHandler(this Control control, MethodInvoker del) // Async. control-invoke extension.
    {
        if (control.InvokeRequired)
        {
            control.BeginInvoke(del);
            return; 
        }
        del(); // run the actual code.
    }
}

样本;

this.TreeView.AsyncInvokeHandler(() =>
        {
            this.Text = 'xyz'
        });

允许跨线程gui更新。

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);
    }
}

如果你有波斯语，并且必须用波斯语向用户显示数字:

static public string ToFaString         (this string value)
        {
            // 1728 , 1584
            string result = "";
            if (value != null)
            {
                char[] resChar = value.ToCharArray();
                for (int i = 0; i < resChar.Length; i++)
                {
                    if (resChar[i] >= '0' && resChar[i] <= '9')
                        result += (char)(resChar[i] + 1728);
                    else
                        result += resChar[i];
                }
            }
            return result;
        }

讨厌这种代码?

CloneableClass cc1 = new CloneableClass ();
CloneableClass cc2 = null;
CloneableClass cc3 = null;

cc3 = (CloneableClass) cc1.Clone (); // this is ok
cc3 = cc2.Clone (); // this throws null ref exception
// code to handle both cases
cc3 = cc1 != null ? (CloneableClass) cc1.Clone () : null;

它有点笨拙，所以我用这个扩展替换它，我称之为CloneOrNull -

public static T CloneOrNull<T> (this T self) where T : class, ICloneable
{
    if (self == null) return null;
    return (T) self.Clone ();
}

用法如下:

CloneableClass cc1 = new CloneableClass ();
CloneableClass cc2 = null;
CloneableClass cc3 = null;

cc3 = cc1.CloneOrNull (); // clone of cc1
cc3 = cc2.CloneOrNull (); // null
// look mom, no casts!

请随意在任何地方使用这个!