Linq – convert system.data.linq.binary to byte[]

linqlinq-to-sql

I am storing bytes in a database table. When I retrieve it with Linq 2 sql I get the return type in system.data.linq.Binary.

I am not able to convert the system.data.linq.binary to byte array(byte[]).

How do I convert it?

///my datacontext

var db = new db();

//key is an value from user

var img = from i in db.images
          where i.id == key
          select i.data;

the i.data is in linq.binary I want it to be in byte[].

I tried with (byte[])img but it did not work.

Best Answer

Have you tried calling ToArray() on i.data?

var img = from i in db.images
      where i.id == key
      select i.data.ToArray();

System.Data.Linq.Binary has a ToArray method just for that purpose.

Related Solutions

.net – do to resolve a “Row not found or changed” Exception in LINQ to SQL on a SQL Server Compact Edition Database

Thats nasty, but simple:

Check if the data types for all fields in the O/R-Designer match the data types in your SQL table. Double check for nullable! A column should be either nullable in both the O/R-Designer and SQL, or not nullable in both.

For example, a NVARCHAR column "title" is marked as NULLable in your database, and contains the value NULL. Even though the column is marked as NOT NULLable in your O/R-Mapping, LINQ will load it successfully and set the column-String to null.

Now you change something and call SubmitChanges().
LINQ will generate a SQL query containing "WHERE [title] IS NULL", to make sure the title has not been changed by someone else.
LINQ looks up the properties of [title] in the mapping.
LINQ will find [title] NOT NULLable.
Since [title] is NOT NULLable, by logic it never could be NULL!
So, optimizing the query, LINQ replaces it with "where 0 = 1", the SQL equivalent of "never".

The same symptom will appear when the data types of a field does not match the data type in SQL, or if fields are missing, since LINQ will not be able to make sure the SQL data has not changed since reading the data.

C# – Max or Default

Since DefaultIfEmpty isn't implemented in LINQ to SQL, I did a search on the error it returned and found a fascinating article that deals with null sets in aggregate functions. To summarize what I found, you can get around this limitation by casting to a nullable within your select. My VB is a little rusty, but I think it'd go something like this:

Dim x = (From y In context.MyTable _
         Where y.MyField = value _
         Select CType(y.MyCounter, Integer?)).Max

Or in C#:

var x = (from y in context.MyTable
         where y.MyField == value
         select (int?)y.MyCounter).Max();

Best Answer

Related Solutions

.net – do to resolve a “Row not found or changed” Exception in LINQ to SQL on a SQL Server Compact Edition Database

C# – Max or Default

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