ExecuteQuery and save the results in a string

Question

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SQL-Server-2008R2

I want to execute a SQL command from c#

I have:

SQL

byte[] md5 = ccDc.ExecuteQuery<byte[]>("SELECT HASHBYTES('MD5', ChunkData) FROM  dbo.x where id={0}", myData.Id).FirstOrDefault();

but it gives me the error :

Quote:
The type 'System.Byte[]' must declare a default (parameterless) constructor in order to be constructed during mapping.

when I execute

SELECT HASHBYTES('MD5', ChunkData) FROM dbo.x where Id = '40'

it shows me the md5 I want to read it in my c# code

Can anybody help me?
Thanks

Posted 9-Oct-15 5:22am

Lalyka

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Sinisa Hajnal 10-Oct-15 9:47am

Try to explicitly define array length

1 solution

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Daniel Miller · Answer 1 · 2015-10-19T05:01:00

Solution 1

Have you tried something along these lines?

C#

var select = "SELECT HASHBYTES('MD5', ChunkData) FROM dbo.x where Id = @ID";
var parameter = new SqlParameter("ID", 40);
var query = context.Database.SqlQuery<byte[]>(select, parameter);
var buffer = query.FirstOrDefault();

If you are not required to use Entity Framework then a solution like this might be another option:
Getting binary data using SqlDataReader

Posted 19-Oct-15 5:01am

Daniel Miller

Updated 19-Oct-15 6:28am

v3

Comments

Richard Deeming 19-Oct-15 11:39am

Your code is vulnerable to SQL Injection[^].

NEVER use string concatenation to build a SQL query. ALWAYS use a parameterized query.

Daniel Miller 19-Oct-15 12:28pm

Well, yes, obviously you would use a parameterized query in a live system. How to do this was not the question being asked, and my solution was intended to illustrate a specific answer to a specific question as simply as possible. Rather than criticize, perhaps you could have posted a helpful amendment like this:

var select = "SELECT HASHBYTES('MD5', ChunkData) FROM dbo.x where Id = @ID";
var parameter = new SqlParameter("ID", 40);
var query = context.Database.SqlQuery<byte[]>(select, parameter);
var buffer = query.FirstOrDefault();

Richard Deeming 19-Oct-15 12:33pm

I'm criticizing because your answer introduced a critical security vulnerability into the code, which was not present in the question. My intention was to get you to update your solution with the corrected code, which you have now done.

Daniel Miller 19-Oct-15 12:42pm

Fair enough - point taken.

Richard Deeming 19-Oct-15 12:43pm

I've updated my vote, but it might take a while to show up due to caching.

Daniel Miller 19-Oct-15 13:21pm

Thanks, I appreciate it. I have been 'lurking' on the CodeProject site for years because it's such a great resource, and recently I decided I ought to begin contributing something back to it, so I am working to develop and improve a reputation in the community here.