我最近正在使用一个DateTime对象，并写了这样的东西:
DateTime dt = DateTime.Now;
dt.AddDays(1);
return dt; // still today's date! WTF?
AddDays()的智能感知文档说它在日期后添加了一天，但它并没有这样做——它实际上返回了一个添加了一天的日期，所以你必须这样写:
DateTime dt = DateTime.Now;
dt = dt.AddDays(1);
return dt; // tomorrow's date
这个问题以前已经困扰过我很多次了，所以我认为将最糟糕的c#陷阱分类会很有用。
当前回答
也许不是最糟糕的，但是。net框架的某些部分使用角度，而其他部分使用弧度(智能感知出现的文档从来没有告诉你是哪个，你必须访问MSDN才能找到)
所有这些都可以通过使用一个Angle类来避免……
其他回答
TextInfo textInfo = Thread.CurrentThread.CurrentCulture.TextInfo;
textInfo.ToTitleCase("hello world!"); //Returns "Hello World!"
textInfo.ToTitleCase("hElLo WoRld!"); //Returns "Hello World!"
textInfo.ToTitleCase("Hello World!"); //Returns "Hello World!"
textInfo.ToTitleCase("HELLO WORLD!"); //Returns "HELLO WORLD!"
是的，这种行为是有记录的，但这并不能证明它是正确的。
合同在流。阅读是我见过很多人被绊倒的东西:
// Read 8 bytes and turn them into a ulong
byte[] data = new byte[8];
stream.Read(data, 0, 8); // <-- WRONG!
ulong data = BitConverter.ToUInt64(data);
这是错误的原因是流。Read最多读取指定的字节数，但完全可以只读取1个字节，即使在流结束前还有7个字节可用。
它看起来与Stream如此相似，这并没有什么帮助。如果没有异常返回，则保证已写入所有字节。上面的代码几乎一直都能工作，这也没有什么帮助。当然，没有现成的、方便的方法来正确地读取N个字节也无济于事。
所以，为了堵住这个漏洞，提高人们的意识，这里有一个正确的方法:
/// <summary>
/// Attempts to fill the buffer with the specified number of bytes from the
/// stream. If there are fewer bytes left in the stream than requested then
/// all available bytes will be read into the buffer.
/// </summary>
/// <param name="stream">Stream to read from.</param>
/// <param name="buffer">Buffer to write the bytes to.</param>
/// <param name="offset">Offset at which to write the first byte read from
/// the stream.</param>
/// <param name="length">Number of bytes to read from the stream.</param>
/// <returns>Number of bytes read from the stream into buffer. This may be
/// less than requested, but only if the stream ended before the
/// required number of bytes were read.</returns>
public static int FillBuffer(this Stream stream,
byte[] buffer, int offset, int length)
{
int totalRead = 0;
while (length > 0)
{
var read = stream.Read(buffer, offset, length);
if (read == 0)
return totalRead;
offset += read;
length -= read;
totalRead += read;
}
return totalRead;
}
/// <summary>
/// Attempts to read the specified number of bytes from the stream. If
/// there are fewer bytes left before the end of the stream, a shorter
/// (possibly empty) array is returned.
/// </summary>
/// <param name="stream">Stream to read from.</param>
/// <param name="length">Number of bytes to read from the stream.</param>
public static byte[] Read(this Stream stream, int length)
{
byte[] buf = new byte[length];
int read = stream.FillBuffer(buf, 0, length);
if (read < length)
Array.Resize(ref buf, read);
return buf;
}
前几天我看到了这个帖子，我觉得它很晦涩，对那些不知道的人来说很痛苦
int x = 0;
x = x++;
return x;
因为这将返回0，而不是大多数人期望的1
[Serializable]
class Hello
{
readonly object accountsLock = new object();
}
//Do stuff to deserialize Hello with BinaryFormatter
//and now... accountsLock == null ;)
这个故事的寓意:反序列化对象时不运行字段初始化程序
mystring.Replace("x","y")
虽然它看起来应该对被调用的字符串进行替换，但实际上它返回了一个新字符串，替换完成后没有改变被调用的字符串。你需要记住字符串是不可变的。
