RE: EF or LINQtoSQL and VarBinary Max?
- From: v-micsun@xxxxxxxxxxxxxxxxxxxx (Lingzhi Sun [MSFT])
- Date: Wed, 26 Aug 2009 06:28:14 GMT
Hi SnapDive,
Gregory is correct that in LINQ to SQL, varbinary(max) is bound to
System.Data.Linq.Binary or byte[], while in LINQ to Entities, it is
generally bound to byte[]. To do CRUD operations on such tables with
varbinary(max) via LINQ to SQL and LINQ to Entities, you can see the
following codes for references:
Here is a helper method to read images into byte[]:
===================================================================
private static byte[] ReadImage(string path)
{
try
{
// Open the image file
using (FileStream fs = new FileStream(path, FileMode.Open,
FileAccess.Read))
{
// Create an array of bytes
byte[] bPicture = new byte[fs.Length];
// Read the image file
fs.Read(bPicture, 0, Convert.ToInt32(fs.Length));
return bPicture;
}
}
catch (Exception ex)
{
Console.WriteLine(
"The application throws the error: {0}", ex.Message);
return null;
}
}
===================================================================
LINQ to SQL: (for Binary, if mapping to byte[], the codes is similar with
the LINQ to Entities part)
===================================================================
Insert:
MyDataContext db = new MyDataContext();
MyImageTable myImage = new MyImageTable()
{
ImageID = 2,
MyImage = ReadImage("C#.jpg")
};
db.MyImageTables.InsertOnSubmit(myImage);
db.SubmitChanges();
Read:
var myImage = db.MyImageTables.Where(i => i.ImageID == 2).Single();
MemoryStream stream = new MemoryStream();
stream.Write(myImage.MyImage.ToArray(), 0, myImage.MyImage.Length);
Image image = Image.FromStream(stream);
Search:
byte[] imageBytes = ReadImage("C#.jpg");
var query = from i in db.MyImageTables
where i.MyImage == imageBytes
select i;
MessageBox.Show(query.First().MyImage.Length.ToString());
Delete:
db.MyImageTables.DeleteOnSubmit(myImage);
db.SubmitChanges();
===================================================================
LINQ to Entities:
===================================================================
Insert:
MyEntities entities = new MyEntities();
MyImageTable myImage = new MyImageTable();
myImage.ImageID = 2;
myImage.MyImage = ReadImage("C#.jpg");
entities.AddToMyImageTable(image);
entities.SaveChanges();
Read:
MemoryStream stream = new MemoryStream();
MyImageTable myImage = entities.MyImageTable.First();
stream.Write(myImage.MyImage, 0, myImage.MyImage.Length);
Image image = Image.FromStream(stream);
Search:
byte[] imageBytes = ReadImage("C#.jpg");
var query = from i in entities.MyImageTable
where i.MyImage == imageBytes
select i;
Delete:
entities.DeleteObject(myImage);
entities.SaveChanges();
===================================================================
If you encounter any problems, please feel free to let me know.
Have a nice day!
Best Regards,
Lingzhi Sun
Microsoft Online Community Support
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