How to Generate unique file names in C#

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I have implemented an algorithm that will generate unique names for files that will save on hard drive. I'm appending DateTime: Hours,Minutes,Second and Milliseconds but still it generates duplicate name of files because im uploading multiple files at a time.

What is the best solution to generate unique names for files to be stored on hard drive so no 2 files are same?

If readability doesn't matter, use GUIDs.

E.g.:

var myUniqueFileName = string.Format(@"{0}.txt", Guid.NewGuid());

or shorter:

var myUniqueFileName = $@"{Guid.NewGuid()}.txt";

In my programs, I sometimes try e.g. 10 times to generate a readable name ("Image1.png"…"Image10.png") and if that fails (because the file already exists), I fall back to GUIDs.

Update:

Recently, I've also use DateTime.Now.Ticks instead of GUIDs:

var myUniqueFileName = string.Format(@"{0}.txt", DateTime.Now.Ticks);

or

var myUniqueFileName = $@"{DateTime.Now.Ticks}.txt";

The benefit to me is that this generates a shorter and "nicer looking" filename, compared to GUIDs.

Please note that in some cases (e.g. when generating a lot of random names in a very short time), this might make non-unique values.

Stick to GUIDs if you want to make really sure that the file names are unique, even when transfering them to other computers.

C#: What is the fastest way to generate a unique filename?, Returns a random folder name or file name. public: static System::String ^ GetRandomFileName();. C# Copy. 3 approaches to generate unique filename in C#. In this article we will show three different approaches to generate random file name In C#. File uploading and handling is very common scenario in project development. And it’s always good practice to change file name after uploading by user.

Use

Path.GetTempFileName()

or use new GUID().

Path.GetTempFilename() on MSDN.

Path.GetRandomFileName Method (System.IO), The only way to guarantee that the generated filename is truly unique is to actually create the file. Any other method is vulnerable to a race� You can have a unique file name automatically generated for you without any custom methods. Just use the following with the StorageFolder Class [1] or the StorageFile Class [2]. The key here is: CreationCollisionOption.GenerateUniqueName and NameCollisionOption.GenerateUniqueName. To create a new file with a unique filename:

System.IO.Path.GetRandomFileName()

Path.GetRandomFileName() on MSDN.

Creating a unique file name in C#, In this article we will show three different approaches to generate random file name In C#. File uploading and handling is very common scenario� My recommendation is to generate the name and create the file only if it doesn't exist. If it does, throw an exception and catch it, then generate a new guid and try again. That way, you have zero chance of errors and can sleep easy at night.

If the readability of the file name isn't important, then the GUID, as suggested by many will do. However, I find that looking into a directory with 1000 GUID file names is very daunting to sort through. So I usually use a combination of a static string which gives the file name some context information, a timestamp, and GUID.

For example:

public string GenerateFileName(string context)
{
    return context + "_" + DateTime.Now.ToString("yyyyMMddHHmmssfff") + "_" + Guid.NewGuid().ToString("N");
}

filename1 = GenerateFileName("MeasurementData");
filename2 = GenerateFileName("Image");

This way, when I sort by filename, it will automatically group the files by the context string and sort by timestamp.

Note that the filename limit in windows is 255 characters.

3 approaches to generate unique filename in C#, I have implemented an algorithm that will generate unique names for files that will save on hard drive. I'm appending DateTime: Hours,Minutes,Second and� Creating a unique file name in C#. Ask Question The only way to guarantee that the generated filename is truly unique is to actually create the file.

Here's an algorithm that returns a unique readable filename based on the original supplied. If the original file exists, it incrementally tries to append an index to the filename until it finds one that doesn't exist. It reads the existing filenames into a HashSet to check for collisions so it's pretty quick (a few hundred filenames per second on my machine), it's thread safe too, and doesn't suffer from race conditions.

For example, if you pass it test.txt, it will attempt to create files in this order:

test.txt
test (2).txt
test (3).txt

etc. You can specify the maximum attempts or just leave it at the default.

Here's a complete example:

class Program
{
    static FileStream CreateFileWithUniqueName(string folder, string fileName, 
        int maxAttempts = 1024)
    {
        // get filename base and extension
        var fileBase = Path.GetFileNameWithoutExtension(fileName);
        var ext = Path.GetExtension(fileName);
        // build hash set of filenames for performance
        var files = new HashSet<string>(Directory.GetFiles(folder));

        for (var index = 0; index < maxAttempts; index++)
        {
            // first try with the original filename, else try incrementally adding an index
            var name = (index == 0)
                ? fileName
                : String.Format("{0} ({1}){2}", fileBase, index, ext);

            // check if exists
            var fullPath = Path.Combine(folder, name);
            if(files.Contains(fullPath))
                continue;

            // try to create the file
            try
            {
                return new FileStream(fullPath, FileMode.CreateNew, FileAccess.Write);
            }
            catch (DirectoryNotFoundException) { throw; }
            catch (DriveNotFoundException) { throw; }
            catch (IOException) 
            {
                // Will occur if another thread created a file with this 
                // name since we created the HashSet. Ignore this and just
                // try with the next filename.
            } 
        }

        throw new Exception("Could not create unique filename in " + maxAttempts + " attempts");
    }

    static void Main(string[] args)
    {
        for (var i = 0; i < 500; i++)
        {
            using (var stream = CreateFileWithUniqueName(@"c:\temp\", "test.txt"))
            {
                Console.WriteLine("Created \"" + stream.Name + "\"");
            }
        }

        Console.ReadKey();
    }
}

c#: How to Generate unique file names in C#, I have implemented an algorithm that will generate unique names for files that will save on hard drive. I'm appending DateTime: Hours,Minutes,Second and� The Random.Next() method returns a random number in C#. The Random class's RandomByte and RandomDouble method returns a random byte and and a random double integer. The code examples show how to generate a random string and random integer in C# and .NET.

How to Generate unique file names in C# - c# - csharp, Generate unique filename everytime. using System; using System.Collections. Generic; using System.Globalization; using System.Linq; using System.Text; using� Unfortunately, these methods cannot help us to create unique temporary folder or temporary file (method Path.GetTempFileName() can generate only 65 536 unique file names at the same time). It is suggested to generate unique path and name to use a globally unique identifier with help of method Guid.NewGuid().

Generate unique filename everytime, First, there are many different ways of generating random strings and file names in the C# language. You could develop a method that populates a char array� A Windows file time is a 64-bit value that represents the number of 100-nanosecond intervals that have elapsed since 12:00 midnight, January 1, 1601 A.D. (C.E.) Coordinated Universal Time (UTC). Windows uses a file time to record when an application creates, accesses, or writes to a file. Source: MSDN documentation - DateTime.ToFileTime Method

C# Path.GetRandomFileName Method, I have implemented an algorithm that will generate unique names for files that will save on hard drive. Im appending DateTime,Hours,Minutes� C# Identifiers. All C# variables must be identified with unique names. These unique names are called identifiers. Identifiers can be short names (like x and y) or more descriptive names (age, sum, totalVolume). Note: It is recommended to use descriptive names in order to create understandable and maintainable code:

Comments
  • It depends on other requirements; this [old] question was/is too vague.
  • I like using Ticks as a GUID is really ugly. You can also get a hash of the Ticks which reduces the character length of the filename. DateTime.Now.Ticks.GetHashCode().ToString("x").ToUpper()
  • "Ticks" is predictable and not thread-safe (as the same 'ticks' can be obtained from multiple threads/processes). This makes it not suitable for temp filename generation. Generating X..1..N may be suitable for user-facing tasks (ie. copy in Explorer), but is dubious for server work.
  • Here is the link to the MSDN doc: msdn.microsoft.com/en-us/library/…
  • Note though, that GetTempFileName() might throw an exception if you create many such files without deleting them.
  • "The GetTempFileName method will raise an IOException if it is used to create more than 65535 files without deleting previous temporary files." says the MSDN article.
  • WARNING: GetTempFileName will create a File. This also means that it chooses the temp path location. On the other hand, GetRandomFileName is suitable to generate a 8.3 filename that can be used with a different path. (I've seen some horrid code that uses GetTempFileName with a File.Delete just to use the filename elsewhere..)
  • Here is the link to the MSDN doc: msdn.microsoft.com/en-us/library/…
  • @RyBolt: Since you don't have to seed yourself there is pretty much nothing you have to keep in mind for using that method. And I'd expect the vast majority of developers to have no clue about how to build secure cryptographic systems.
  • +1 For the suggestion to include useful information combined with a GUID. - An aside to take with a grain of salt: including the date and time in a file name is kind of redundant when you can just Right Click > Sort By > Date.
  • The time becomes useful if you're storing a bunch of files with different contexts in the same directory. Of course, the file name generation should be adjusted based on your specific needs.
  • Should be Guid.NewGuid().ToString();. Missing parenthesis. +1 otherwise
  • This is very slick. Timestamp and Guid. +1
  • I like this solution +1, I added a second parameter string extension which I add to the fileName, this further supports the idea of context and allows to easily open the file with the default application on double click if necessary