How do you generate a unique file name to avoid overwriting an existing one?

Question

ICSM Computer · Answer

To generate a unique file name and avoid overwriting an existing file in C#, you can use a combination of the file name, a
timestamp, a GUID, or an incremental suffix.
Option 1: Add a timestamp to the file name
string baseName = "report";
string extension = ".txt";
string timestamp = DateTime.Now.ToString("yyyyMMdd_HHmmss");
string uniqueFileName = $"{baseName}_{timestamp}{extension}";
// Example result: report_20250513_163015.txt
Option 2: Use a GUID
string uniqueFileName = $"report_{Guid.NewGuid()}.txt";
// Example result: report_3f9c2f1e-874a-42c2-938e-fcf32b73e4cb.txt
Option 3: Check and add a numeric suffix
string directory = @"C:\Reports";
string baseName = "report";
string extension = ".txt";
string path = Path.Combine(directory, baseName + extension);
int count = 1;
while (File.Exists(path))
{
    path = Path.Combine(directory, $"{baseName}_{count}{extension}");
    count++;
}
// 'path' is now a unique file path
File.WriteAllText(path, "Report content");
Option 4: Use Path.GetTempFileName() (for temp files)
string tempFilePath = Path.GetTempFileName();
// Creates a unique, empty temp file with a .tmp extension
Summary:
Strategy
Best For
Timestamp
Human-readable versioning
GUID
Guaranteed uniqueness
Numeric Suffix
Familiar file naming for users
Temp File
Temporary work files
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How do you generate a unique file name to avoid overwriting an existing one?

ICSM Computer

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1 Answers

Option 1: Add a timestamp to the file name

Option 2: Use a GUID

Option 3: Check and add a numeric suffix

Option 4: Use `Path.GetTempFileName()` (for temp files)

Summary:

Liked By

Strategy	Best For
Timestamp	Human-readable versioning
GUID	Guaranteed uniqueness
Numeric Suffix	Familiar file naming for users
Temp File	Temporary work files