How Do I Insert a Byte[] Into an SQL Server VARBINARY Column

Try this:

"0x" + BitConverter.ToString(arraytoinsert).Replace("-", "")

Although you should really be using a parameterised query rather than string concatenation of course...

My solution would be to use a parameterised query, as the connectivity objects take care of formatting the data correctly (including ensuring the correct data-type, and escaping "dangerous" characters where applicable):

// Assuming "conn" is an open SqlConnectionusing(SqlCommand cmd = new SqlCommand("INSERT INTO mssqltable(varbinarycolumn) VALUES (@binaryValue)", conn)){    // Replace 8000, below, with the correct size of the field    cmd.Parameters.Add("@binaryValue", SqlDbType.VarBinary, 8000).Value = arraytoinsert;    cmd.ExecuteNonQuery();}

Edit: Added the wrapping "using" statement as suggested by John Saunders to correctly dispose of the SqlCommand after it is finished with

No problem if all the arrays you are about to use in this scenario are small like in your example.

If you will use this for large blobs (e.g. storing large binary files many Mbs or even Gbs in size into a VARBINARY) then you'd probably be much better off using specific support in SQL Server for reading/writing subsections of such large blobs. Things like READTEXT and UPDATETEXT, or in current versions of SQL Server SUBSTRING.

For more information and examples see either my 2006 article in .NET Magazine ("BLOB + Stream = BlobStream", in Dutch, with complete source code), or an English translation and generalization of this on CodeProject by Peter de Jonghe. Both of these are linked from my weblog.