blob field with compression data is not valid

Generally speaking, this is a practical demonstration of how you can perform any kind of task prior to binding data. So, to create a valid object, you must skip those bytes and pass the excerpt to the Bitmap's constructor. Unfortunately, this is not the case with Northwind, in which images are prefixed with a 78-byte header. Normally, the database BLOB field contains only the image itself. Instead, wrapping the same bytes into a stream object meets the expectations of at least one constructor of the Bitmap class. NET you can't create graphic objects directly from an array of bytes. The array of bytes read from the SQL Serve r table is first copied into a MemoryStream object. Ms.Write(img, offset, img.Length - offset) Private void PictureFormat(object sender, ConvertEventArgs e) The event handler does the job of transforming an array of bytes into a Bitmap object that can be safely assigned to the Image property of a PictureBox control. So your code would look something like this :īinding bdPhoto = new Binding('Image',_dataSet,'Employees.Photo') īdPhoto.Format += new ConvertEventHandler(this. Nevertheless, the Format event lets you easily accomplish the tasks. The net effect of all these issues is that you need more than a simple conversion to successfully bind to images. To make things even more interesting, the Northwind's Employees pictures need some work to become really usable. The exception originates from a clear incompatibility between the desired type ( ) and the contents of the Photo field, which is resolved to System.Byte. If you try to bind the Employees.Photo column to the Image property of a PictureBox, you get an exception. The Windows Forms data binding works fine with BLOB fields (that is, images), but not in the default way. If you are using a DataSet, you can retrieve an employee's name and photo by using a simple command such as SELECT name, photo FROM employees WHERE id = 1. The following example shows how to retrieve Image data from the SQL Server database Northwind and displaying it in the Windows Form Control PictureBox.

Image - The Image data type can store up to 2GB of binary data, which also enables it to store standard text data.

nText - The nText data type can accommodate up to 1GB of Unicode text data.

Text - The Text data type can accommodate up to 2GB of non-Unicode text data.

SQL Server used three different data types for BLOB storage: Althoug h the database is fully capable of storing BLOB data, the potential size of these objects means that they must be accessed and managed differently than standard text and numeric data types. BLOBs are typically graphical images such as photos contained in. It's common for modern databases to contain large binary objects, more commonly referred to as BLOB's (Binary Large Objects).

Blob field with compression data is not valid