Thumbnails

• Feb 02, 2023
• 2 minutes to read

Image Thumbnails

FileManager automatically creates thumbnails for image files with the following file extensions:

• bmp
• gif
• ico
• jpg
• jpeg
• png

For better performance, these content-based thumbnails are stored in the location specified via the FileManagerSettings.ThumbnailFolder (via the FileManagerSettings.Settings.ThumbnailFolder) property.

Note

The folder that contains thumbnails must be placed physically inside the application folder.

Default Thumbnails

FileManager provides the default thumbnails for some file types listed below.

File Extension	Default Thumbnail
txt
rtf doc docx odt
xls xlsx ods
ppt pptx odp
pdf
other extensions, where thumbnails are not defined

You can change the last thumbnail via the FileManagerImages.File (via the FileManagerSettings.Images.File) property.

Custom Thumbnails

In addition to an automatically created and default thumbnails, FileManager allows you to provide custom thumbnails by handling the server-side FileManagerSettings.CustomThumbnail event. This event allows you to define a custom manner in which all or certain files should be visually represented in folders. Within the event’s handler, a currently processed item can be accessed and identified by using the FileManagerThumbnailCreateEventArgs.Item property, and a custom thumbnail can be defined for the file via the FileManagerThumbnailCreateEventArgs.ThumbnailImage property.

In the example below, the CustomThumbnail event is handled to analyze file extensions and represent each file type using the corresponding custom thumbnail image.

View code:

C#

@model string

@Html.DevExpress().FileManager(settings =>
{
    settings.Name = "FileManager";
    settings.CallbackRouteValues = new { Controller = "Home", Action = "FileManagerPartial" };
    settings.Settings.ThumbnailFolder = Url.Content(@"~/Content/Thumbnails");

    settings.CustomThumbnail = (s, e) =>
    {
        switch(((FileManagerFile)e.Item).Extension)
        {
            case ".avi":
                e.ThumbnailImage.Url = @"~/Images/movie.png";
                break;
            case ".zip":
                e.ThumbnailImage.Url = @"~/Images/archive.png";
                break;
            case ".txt":
                e.ThumbnailImage.Url = @"~/Images/txt.png";
                break;
            case ".rtf":
                e.ThumbnailImage.Url = @"~/Images/richtxt.png";
                break;
            case ".mp3":
                e.ThumbnailImage.Url = @"~/Images/music.png";
                break;
            case ".xml":
                e.ThumbnailImage.Url = @"~/Images/code.png";
                break;
        }
    };
    settings.SettingsFileList.View = DevExpress.Web.FileListView.Thumbnails;
}).BindToFolder(Model).GetHtml()