Coalesce supports the uploading and downloading of files and images through the IntelliTect.Coalesce.DataAnnotations.FileAttribute annotation.


This attribute is currently only supported by the Knockout client stack. It is unsupported in Vue.


Storing large binary objects in relational databases comes with significant performance drawbacks. Use this attribute sparingly, and try to avoid using it for files bigger than a few dozen kilobytes.


To upload a file in Coalesce, consider using Custom Methods instead.

Example Usage

public class Product
    public int ProductId { get; set; }

    public string ProductName { get; set; }

    public byte[] ProductDescription { get; set; }

    public byte[] ProductThumbnail { get; set; }

    public byte[] BinaryDriverFile { get; set; }

Additionally, Coalesce can store file metadata in optional properties that are specified on the attribute's properties. Security information can also be specified with property-level Security Attributes. In the example below, the file can be viewed/downloaded by any user, but only users with the role of "Admin" or "Vendor" will be able to upload a new file.

[Edit(Roles = "Admin,Vendor")]
[File("video/mp4", nameof(VideoName), nameof(VideoHash), nameof(VideoSize))]
public byte[] InstallationVideo { get; set; }

public string VideoName
    get { return "Product" + ProductId + ".mp4" }
public long VideoSize { get; set; }
public string VideoHash { get; set; }

The [InternalUse] attribute can be used in conjunction with IntelliTect.Coalesce.DataAnnotations.FileAttribute. In the example below, Coalesce will store the uploaded filename and provide it again as the name of a file download, but the property itself won't actually get exposed on the DTOs via the API.

[File(NameProperty = nameof(InternalUseFileName))]
public byte[] File { get; set; }

public string InternalUseFileName { get; set; }


public string MimeType { get; set; }

The system will identify the nature and format of the file using the type described in the 'MimeType' property. By default it is set to "application/octet-stream" to read/write the file as an unknown binary file.

An image preview will be displayed for properties annotated with the File attribute whose MIME type contains "image". Other MIME types will result in a download button being displayed.


If a filename exists on the uploaded file, the MIME type may inferred from the file extension and MimeType need not be specified.

public string NameProperty { get; set; }
A property to store the filename into. If the specified property has no setter, this will return a computed filename and the name of the uploaded file will not be used. If the property does have a setter, the property will be populated by the filename on upload.
public string HashProperty { get; set; }
The name of the property to store the hash of Byte[]. This is set upon file upload.
public string SizeProperty { get; set; }
A property to store the size of the file into. This is set upon file upload.