Rename a file in C#

public void RenameFile(string filePath, string newName)
{
    FileInfo fileInfo = new FileInfo(filePath);
    fileInfo.MoveTo(fileInfo.Directory.FullName + "\\" + newName);
}

None of the answers mention writing a unit testable solution. You could use System.IO.Abstractions as it provides a testable wrapper around FileSystem operations, using which you can create a mocked file system objects and write unit tests.

using System.IO.Abstractions;

IFileInfo fileInfo = _fileSystem.FileInfo.FromFileName("filePathAndName");
fileInfo.MoveTo(Path.Combine(fileInfo.DirectoryName, newName));

It was tested, and it is working code to rename a file.

I couldn't find an approach which suits me, so I propose my version. Of course, it needs input and error handling.

public void Rename(string filePath, string newFileName)
{
    var newFilePath = Path.Combine(Path.GetDirectoryName(filePath), newFileName + Path.GetExtension(filePath));
    System.IO.File.Move(filePath, newFilePath);
}

In my case, I want the name of the renamed file to be unique, so I add a date-time stamp to the name. This way, the filename of the 'old' log is always unique:

if (File.Exists(clogfile))
{
    Int64 fileSizeInBytes = new FileInfo(clogfile).Length;
    if (fileSizeInBytes > 5000000)
    {
        string path = Path.GetFullPath(clogfile);
        string filename = Path.GetFileNameWithoutExtension(clogfile);
        System.IO.File.Move(clogfile, Path.Combine(path, string.Format("{0}{1}.log", filename, DateTime.Now.ToString("yyyyMMdd_HHmmss"))));
    }
}

// Source file to be renamed  
string sourceFile = @"C:\Temp\MaheshChand.jpg";  
// Create a FileInfo  
System.IO.FileInfo fi = new System.IO.FileInfo(sourceFile);  
// Check if file is there  
if (fi.Exists)  
{  
// Move file with a new name. Hence renamed.  
fi.MoveTo(@"C:\Temp\Mahesh.jpg");  
Console.WriteLine("File Renamed.");  
}  

public static class ImageRename
{
    public static void ApplyChanges(string fileUrl,
                                    string temporaryImageName,
                                    string permanentImageName)
    {
        var currentFileName = Path.Combine(fileUrl,
                                           temporaryImageName);

        if (!File.Exists(currentFileName))
            throw new FileNotFoundException();

        var extention = Path.GetExtension(temporaryImageName);
        var newFileName = Path.Combine(fileUrl,
                                       $"{permanentImageName}
                                         {extention}");

        if (File.Exists(newFileName))
            File.Delete(newFileName);

        File.Move(currentFileName, newFileName);
    }
}

I've encountered a case when I had to rename the file inside the event handler, which was triggering for any file change, including rename, and to skip forever renaming of the file I had to rename it, with:

1. Making its copy
2. Removing the original

File.Copy(fileFullPath, destFileName); // Both have the format of "D:\..\..\myFile.ext"
Thread.Sleep(100); // Wait for the OS to unfocus the file
File.Delete(fileFullPath);

private static void Rename_File(string FileFullPath, string NewName) // nes name without directory actualy you can simply rename with fileinfo.MoveTo(Fullpathwithnameandextension);
        {
            FileInfo fileInfo = new FileInfo(FileFullPath);
            string DirectoryRoot = Directory.GetParent(FileFullPath).FullName;

            string filecreator = FileFullPath.Substring(DirectoryRoot.Length,FileFullPath.Length-DirectoryRoot.Length);
             
            filecreator = DirectoryRoot + NewName;
            try
            {
                fileInfo.MoveTo(filecreator);
            }
            catch(Exception ex)
            {
                Console.WriteLine(filecreator);
                Console.WriteLine(ex.Message);
                Console.ReadKey();
            }

    enter code here
            // string FileDirectory = Directory.GetDirectoryRoot()

        }