File.SetLastWriteTime() Method in C# with Examples

File.SetLastWriteTime(String) is an inbuilt File class method which is used to set the date and time that the specified file was last written to.

Syntax:

public static void SetLastWriteTime (string path, DateTime lastWriteTime);

Parameter: This function accepts two parameters which are illustrated below: 

• path: This is the specified file for which to set the date and time information.
• lastWriteTime: This is the specified local last write date and time of the path.

Exceptions:

• ArgumentException: The path is a zero-length string, contains only white space, or one or more invalid characters as defined by InvalidPathChars.
• ArgumentNullException: The path is null.
• PathTooLongException: The specified path, file name, or both exceed the system-defined maximum length.
• FileNotFoundException: The specified path was not found.
• UnauthorizedAccessException: The caller does not have the required permission.
• NotSupportedException: The path is in an invalid format.
• ArgumentOutOfRangeException: The lastWriteTime specifies a value outside the range of dates or times permitted for this operation.

Below are the programs to illustrate the File.SetLastWriteTime(String, DateTime) method.
Program 1: Before running the below code, a file file.txt is created with some contents shown below- 

CSharp

// C# program to illustrate the usage
// of File.SetLastWriteTime() method

// Using System and System.IO namespaces
using System;
using System.IO;

class GFG {
    public static void Main()
    {
        // Specifying a file
        string myfile = @"file.txt";

        // Calling the SetLastWriteTime() function
        // to set last written date and time
        File.SetLastWriteTime(myfile, new DateTime(2020,
                                         5, 4, 4, 5, 7));

        // Getting the last written date and time
        // of the file
        DateTime dt = File.GetLastWriteTime(myfile);
        Console.WriteLine("The last written date and "+
                     "time for this file was {0}.", dt);
    }
}

Output:

The last written date and time for this file was 5/4/2020 4:05:07 AM.

Program 2: Initially, no file was created. Below code, itself creates a file file.txt and prints the last written date and time.

CSharp

// C# program to illustrate the usage
// of File.SetLastWriteTime() method

// Using System and System.IO namespaces
using System;
using System.IO;

class GFG {
    public static void Main()
    {
        // Specifying a file
        string path = @"file.txt";

        // Checking the existence of the file
        if (!File.Exists(path)) {
            File.Create(path);
        }

        // Calling the SetLastWriteTime() function
        // to set last written date and time
        File.SetLastWriteTime(path, new DateTime(2019,
                                      5, 4, 4, 5, 7));

        // Getting the last written date and time
        // of the specified file
        DateTime dt = File.GetLastWriteTime(path);
        Console.WriteLine("The last written date and "+
                     "time for this file was {0}.", dt);
    }
}

Executing:

The last written date and time for this file was 5/4/2019 4:05:07 AM.