Change created by,modifed by,created and modified values of a file programatically in SharePoint

In some scenario's while uploading a file to share point library we need to change the created by,modifed by,created and modified values. If you try to upload document directly, it shows current user name for createdby/modifiedby fileds and current datetime for created/modified fileds.

static void Main(string[] args)
{
    string uploadFile = @"C:\SampleFile.txt";
    string siteURL = "http://YourSharepointsiteURL";
    string docLibraryName = "Shared Documents";

    using (SPSite objSite = new SPSite(siteURL))
    {
      using (SPWeb objWeb = objSite.OpenWeb())
       {
        if (!System.IO.File.Exists(uploadFile))
            throw new FileNotFoundException("File not found.", uploadFile);

    SPFolder myLibrary = objWeb.Folders[docLibraryName];
    
    bool replaceExistingFiles = true;
    string fileName = System.IO.Path.GetFileName(uploadFile);
    SPUser user = objWeb.EnsureUser("username");
    //For  "Created By" and " Modified By" the values are stored in format "ID;#LoginName", so create the same format
    string userIDHashName = user.ID + ";#" + user.Name;

    FileStream fileStream = File.OpenRead(uploadFile);   
    // add document to library
    SPFile spfile = myLibrary.Files.Add(fileName, fileStream,replaceExistingFiles);
    spfile.Item["Created"] = DateTime.Now.AddDays(-1);
    spfile.Item["Modified"] = DateTime.Now.AddDays(-2);
    spfile.Item["Created By"] = userIDHashName;
    spfile.Item["Modified By"] = userIDHashName;

    // update libary
    spfile.Item.Update();
    // update libary 
    myLibrary.Update();
   
    }
    }
}

Note: The username user should exsists in site users otherwise if you provide invalid user for Created By/Modifed By we will get exception.
Hope this works!