The namespaces conception in C# seems to be exhaustive and insufficient at the same time compared with a strong module notation in Oberon-2 and even with a modular programming approaches in Free Pascal/Delphi.
Why insufficient? You cannot declare constants and functions within namespaces but you should add a class with constant field or static method for it.
Why exhaustive? The using directive with such introduced classes is the source of unexpected errors. Here is an example below.
How to insert fast a file (i.e. binary one) from disk to a SQL Server table?
Certainly the SQL Server account should have a corresponding permissions to access the file on the disk. For example I take the file C:\WINDOWS\system32\oembios.bin having the size about 12 MB. For really big files you'd better switch to the FILESTREAM approach.