blocks|key|2920398|text|你可以试试writer.BaseStream.SetLength(writer.BaseStream.Position)，尽管我不确定它会有多好。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2920399|对于FileStream，我认为这应该将文件截断到当前位置。|2920400|entityMap^0|5|1J|0|0^^$0|@$1|2|3|4|5|6|7|J|8|@$9|K|A|L|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|M|8|@]|D|@]|E|$]]|$1|H|3|-4|5|6|7|N|8|@]|D|@]|E|$]]]|I|$]]

you could try <code>writer.BaseStream.SetLength(writer.BaseStream.Position)</code> although I'm not sure how well that would work.

For a FileStream I think that should truncate the file to the current position.

blocks|key|248317|text|使用SetLength设置文件的新长度-文件应被截断。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|248318|请参阅相关问题的this+answer。|248319|entityMap|0|LINK|mutability|MUTABLE|url|http://msdn.microsoft.com/en-us/library/system.io.filestream.setlength.aspx|1|https://stackoverflow.com/questions/8288401/c-sharp-filestream-both-lock-a-file-and-at-the-same-time-be-able-to-read-it-w/8288413#8288413^0|2|9|2|9|0|0|8|B|1|0^^$0|@$1|2|3|4|5|6|7|R|8|@$9|S|A|T|B|C]]|D|@$9|U|A|V|1|W]]|E|$]]|$1|F|3|G|5|6|7|X|8|@]|D|@$9|Y|A|Z|1|10]]|E|$]]|$1|H|3|-4|5|6|7|11|8|@]|D|@]|E|$]]]|I|$J|$5|K|L|M|E|$N|O]]|P|$5|K|L|M|E|$N|Q]]]]

Use <a href="http://msdn.microsoft.com/en-us/library/system.io.filestream.setlength.aspx" rel="nofollow noreferrer"><code>SetLength</code></a> to set the new length of the file - the file should get truncated.

See <a href="https://stackoverflow.com/questions/8288401/c-sharp-filestream-both-lock-a-file-and-at-the-same-time-be-able-to-read-it-w/8288413#8288413">this answer</a> to a related question.

blocks|key|245484|text|如果日志文件的大小超过1+MB，此代码将截断该文件的一部分。|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|245485|using+(FileStream+fs+=+File.Open("C:\\LogFile.txt",+FileMode.OpenOrCreate))
++++++++{
++++++++++++int+OneMB+=+1000000;

++++++++++++fs.Seek(0,+SeekOrigin.Begin);
++++++++++++if+(fs.Length+>+OneMB)
++++++++++++{+
++++++++++++++++int+fileByte+=+1;
++++++++++++++++fs.Position++=+fs.Seek(fs.Length+/+2,+SeekOrigin.Begin);
++++++++++++++++List<byte>+bytes+=+new+List<byte>();

++++++++++++++++while+(fileByte+>+0)
++++++++++++++++{
+++++++++++++++++++fileByte+=+fs.ReadByte();
+++++++++++++++++++bytes.Add((byte)fileByte);
++++++++++++++++}

++++++++++++++++fs.SetLength(0);
++++++++++++++++fs.Position+=+0;
++++++++++++++++fs.Write(bytes.ToArray(),+0,+bytes.Count());

++++++++++++++++fs.Seek(0,+SeekOrigin.End);
++++++++++++++++var+stringBytes+=++UTF8Encoding.ASCII.GetBytes($"Test1"+%2B+Environment.NewLine);
++++++++++++++++fs.Write(stringBytes,+0,+stringBytes.Length);++
++++++++++++}
++++++++++++else
++++++++++++{
++++++++++++++++fs.Seek(0,+SeekOrigin.End);
++++++++++++++++var+stringBytes+=+UTF8Encoding.ASCII.GetBytes($"Test2"+%2B+Environment.NewLine);
++++++++++++++++fs.Write(stringBytes,+0,+stringBytes.Length);+
++++++++++++}

++++++++++++fs.Flush();
++++++++}
++++}|code-block|syntax|javascript|245486|entityMap^0|G|E|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|P|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|L|$]]

This code will truncate part of the log file, if the file grows above 1 MB.

<pre><code>using (FileStream fs = File.Open("C:\\LogFile.txt", FileMode.OpenOrCreate))
 {
 int OneMB = 1000000;

 fs.Seek(0, SeekOrigin.Begin);
 if (fs.Length &gt; OneMB)
 { 
 int fileByte = 1;
 fs.Position = fs.Seek(fs.Length / 2, SeekOrigin.Begin);
 List&lt;byte&gt; bytes = new List&lt;byte&gt;();

 while (fileByte &gt; 0)
 {
 fileByte = fs.ReadByte();
 bytes.Add((byte)fileByte);
 }

 fs.SetLength(0);
 fs.Position = 0;
 fs.Write(bytes.ToArray(), 0, bytes.Count());

 fs.Seek(0, SeekOrigin.End);
 var stringBytes = UTF8Encoding.ASCII.GetBytes($"Test1" + Environment.NewLine);
 fs.Write(stringBytes, 0, stringBytes.Length); 
 }
 else
 {
 fs.Seek(0, SeekOrigin.End);
 var stringBytes = UTF8Encoding.ASCII.GetBytes($"Test2" + Environment.NewLine);
 fs.Write(stringBytes, 0, stringBytes.Length); 
 }

 fs.Flush();
 }
 }
</code></pre>

<pre><code>var fs = new FileStream(filePath, FileMode.OpenOrCreate, FileAccess.ReadWrite);
using(var writer = new StreamWriter(fs))
 writer.Write(....);
</code></pre>

If the file previously contained text and the newly-written text is shorter than what was already in the file, how do I make sure that the obsolete trailing content in the file is truncated?

Note that opening the file in truncate mode isn't an option in this case. The file is already open when I receive the <code>FileStream</code> object. The above code is just to illustrate the stream's properties.

EDIT

Expanding on the answer below, the solution is:

<pre><code>var fs = new FileStream(filePath, FileMode.OpenOrCreate, FileAccess.ReadWrite);
using(var writer = new StreamWriter(fs))
{
 writer.Write(....);
 writer.Flush();
 fs.SetLength(fs.Position);
}
</code></pre>

FileStream and StreamWriter - How to truncate the remainder of the file after writing?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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var fs = new FileStream(filePath, FileMode.OpenOrCreate, FileAccess.ReadWrite);using(var writer = new StreamWriter(fs))    writer.Write(....);如果文件以前包含的文本和新编写的文本...

问FileStream和StreamWriter -如何在写入后截断文件的其余部分？
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问FileStream和StreamWriter -如何在写入后截断文件的其余部分？EN