LastWriteTime Property

FileSystemInfo.LastWriteTime Property


Gets or sets the time when the current file or directory was last written to.

Namespace:   System.IO
Assembly:  mscorlib (in mscorlib.dll)

public DateTime LastWriteTime { get; set; }

Property Value

Type: System.DateTime

The time the current file was last written.

Exception Condition

Refresh cannot initialize the data.


The current operating system is not Windows NT or later.


The caller attempts to set an invalid write time.

Note   This method may return an inaccurate value, because it uses native functions whose values may not be continuously updated by the operating system.

The value of the LastWriteTime property is pre-cached if the current instance of the FileSystemInfo object was returned from any of the following DirectoryInfo methods:

To get the latest value, call the Refresh method.

If the file described in the FileSystemInfo object does not exist, this property will return 12:00 midnight, January 1, 1601 A.D. (C.E.) Coordinated Universal Time (UTC), adjusted to local time.

This property value is null if the file system containing the file does not support this information.


These operating systems do not support this property, and DirectoryInfo implementations of this property are not supported.

The following code example demonstrates the updating of the LastWriteTime property through a "touch" operation. In this example, the file is "touched", updating the CreationTime, LastAccessTime and LastWriteTime properties to the current date and time.

using System;
using System.IO;

namespace touch
    class Touch
        static void Main(string[] args)
            // Make sure a filename was provided.
            if (args.Length > 0)
                // Verify that the provided filename exists.
                if (File.Exists(args[0]))
                    FileInfo fi = new FileInfo(args[0]);
                        "Could not find the file: {0}.", args[0]);
                Console.WriteLine("No file was specified.");

        static void touchFile(FileSystemInfo fsi)
            Console.WriteLine("Touching: {0}", fsi.FullName);

            // Update the CreationTime, LastWriteTime and LastAccessTime.
                fsi.CreationTime = fsi.LastWriteTime = fsi.LastAccessTime =
            catch (Exception e)
                Console.WriteLine("Error: {0}", e.Message);


for setting the last write time. Associated enumeration: FileIOPermissionAccess.Write

Universal Windows Platform
Available since 10
.NET Framework
Available since 1.1
Available since 2.0
Windows Phone Silverlight
Available since 7.0
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