如何检查文件是否存在于 UNC 路径中？

Question

Im trying to check the presence of the file in a UNC path using the File.Exist() func in c#, But even if the file is present it returns only as false.

Following is the sample code

outPath="\\DevSrv\\outPath\\result.txt";
if(File.Exists(outPath))
{
 .....
}

The above code always fails event the path "\DevSrv\outPath\result.txt" is valid. I am able to access the path using the windows explorer.

---

Sorry i missed the "\" while creating this post

Answer 1

Use @ before your string for avoid having to escape slashes

outPath=@"\\DevSrv\outPath\result.txt";
if(File.Exists(outPath))
{
  .....
}

Answer 2

You aren't escaping the slashes, try:

outPath="\\\\DevSrv\\outPath\\result.txt";
if(File.Exists(outPath))
{
    .....
}

Answer 3

When using strings with a backslash you need to think about escape sequence. This link will give you a detailed view about the escape sequences. http://blogs.msdn.com/b/csharpfaq/archive/2004/03/12/what-character-escape-sequences-are-available.aspx

Quote from link :

C# defines the following character escape sequences:

• \\' - single quote, needed for character literals
• \\" - double quote, needed for string literals
• \\\\ - backslash
• \\0 - Unicode character 0
• \\a - Alert (character 7)
• \\b - Backspace (character 8)
• \\f - Form feed (character 12)
• \\n - New line (character 10)
• \\r - Carriage return (character 13)
• \\t - Horizontal tab (character 9)
• \\v - Vertical quote (character 11)
• \\uxxxx - Unicode escape sequence for character with hex value xxxx
• \\xn[n][n][n] - Unicode escape sequence for character with hex value nnnn (variable length version of \\uxxxx)
• \\Uxxxxxxxx - Unicode escape sequence for character with hex value xxxxxxxx (for generating surrogates)

Of these, \\a, \\f, \\v, \\x and \\U are rarely used in my experience.

So in your example. You can use the following options for your string.

outPath=@"\\DevSrv\outPath\result.txt";
//Or
outPath="\\\\DevSrv\\outPath\\result.txt";

Answer 4

There's a difference between UNC and regular paths.

considuring having a file:

c:\temp\myFile.txt

Testing for

File.Exists(@"c:\temp\myFile.txt") 

will return true.

But even the following (having double backslashes)

File.Exists(@"c:\temp\\myFile.txt")  

returns true.

BUT using UNC + having doubleSlashes

File.Exists(@"\\?\c:\temp\\myFile.txt")  

returns false

So - as many mentioned - using

Path.Combine()

is a good habit since it makes sure you don't have these double slashes.