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Display an OLE Object from a Microsoft Access Database using OLE Stripper

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Display an OLE Object from a Microsoft Access Database using OLE Stripper

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In database programming, it happens a lot that you need to bind a picture box to a field with type of photo or image. For example, if you want to show an Employee’s picture from Northwind.mdb database, you might want to try the following code:

picEmployees.DataBindings.Add(“Image”, bsEmployees, “Photo”, true);

This code works if the images are stored in the database with no OLE header or the images stored as a raw image file formats. As the pictures stored in the Northwind database in are not stored in raw image file formats and they are stored as an OLE image documents, then you have to strip off the OLE header to work with the image properly.

Binding imageBinding = new Binding("Image", bsEmployees,
                                   "ImageBlob.ImageBlob", true);
imageBinding.Format += new ConvertEventHandler(this.PictureFormat);
 
private void PictureFormat(object sender, ConvertEventArgs e)
{
    Byte[] img = (Byte[])e.Value;
    MemoryStream ms = new MemoryStream();
    int offset = 78;
    ms.Write(img, offset, img.Length - offset);
    Bitmap bmp = new Bitmap(ms);
    ms.Close();
    // Writes the new value back
    e.Value = bmp;
}

Fortunately, there are some overload methods in .NET Framework to take care of this mechanism, but it cannot be guaranteed whether you need to strip off the OLE object by yourself or not. For example, you can use the following technique to access the images of the Northwind.mdb that ships with Microsoft Access and they will be rendered properly.

picEmployees.DataBindings.Add(“Image”, bsEmployees, “Photo”, true,
DataSourceUpdateMode.Never, new Bitmap(typeof(Button), “Button.bmp”));

Unfortunately, there are some scenarios that you need a better solution. For example, the Xtreme.mdb database that ships with Crystal Reports has a photo filed that cannot be handled by the preceding methods. For these complex scenarios, you can download the OLEStripper classes from here and re-write the PictureFormat method as it is shown below:

private void PictureFormat(object sender, ConvertEventArgs e)
{
     // photoIndex is same as Employee ID
     int photoIndex = Convert.ToInt32(e.Value);
     // Read the original OLE object
     ReadOLE olePhoto = new ReadOLE();
 
     string PhotoPath = olePhoto.GetOLEPhoto(photoIndex);
 
     // Strip the original OLE object
     StripOLE stripPhoto = new StripOLE();
 
     string StripPhotoPath = stripPhoto.GetStripOLE(PhotoPath);
 
     FileStream PhotoStream = new FileStream(StripPhotoPath
                                           , FileMode.Open);
 
     Image EmployeePhoto = Image.FromStream(PhotoStream);
 
     e.Value = EmployeePhoto;
 
     PhotoStream.Close();
 
}

 

 

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Published at DZone with permission of Amir Ahani, DZone MVB. See the original article here.

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