Question

What I am trying to do is create some arbitrary sql command with parameters, set the values and types of the parameters, and then return the parsed sql command – with parameters included. I will not be directly running this command against a sql database, so no connection should be necessary. So if I ran the example program below, I would hope to see the following text (or something similar):

WITH SomeTable (SomeColumn)
AS
(
    SELECT N':)'
    UNION ALL
    SELECT N'>:o'
    UNION ALL
    SELECT N'^_^'
)
SELECT SomeColumn FROM SomeTable

And the sample program is:

using System;
using System.Data;
using System.Data.SqlClient;

namespace DryEraseConsole
{
    class Program
    {
        static void Main(string[] args)
        {
            const string COMMAND_TEXT = @"
WITH SomeTable (SomeColumn)
AS
(
    SELECT N':)'
    UNION ALL
    SELECT N'>:o'
    UNION ALL
    SELECT @Value
)
SELECT SomeColumn FROM SomeTable
";
            SqlCommand cmd = new SqlCommand(COMMAND_TEXT);
            cmd.CommandText = COMMAND_TEXT;
            cmd.Parameters.Add(new SqlParameter
            {
                ParameterName = "@Value",
                Size = 128,
                SqlDbType = SqlDbType.NVarChar,
                Value = "^_^"
            });
            Console.WriteLine(cmd.CommandText);
            Console.ReadKey();
        }
    }
}

Is this something that is achievable using the .net standard libraries? Initial searching says no, but I hope I’m wrong.

Answer 1

You have a mistaken notion of how parameterized queries work. The “parsed text” you speak of is never created, and parameter values are never substituted directly into the query string.

That’s why it’s so important to use parameterized queries — you have complete segregation of query data from query code. Data is data, code is code, and never the twain shall meet. Thus, there is no possibility for sql injection.

What it means is that if you have a CommandText like this:

SELECT SomeColumn FROM SomeTable WHERE ID= @ID

instead of ultimately running a query that looks like this:

SELECT SomeColumn FROM SomeTable WHERE ID= 123

you actually run something more like this:

DECLARE @ID Int
Set @ID = RetrieveQueryDataItem("@ID")
SELECT SomeColumn FROM SomeTable WHERE ID= @ID

Now, this isn’t exactly what happens; the engine doesn’t transform the code like that. Instead, it uses the sp_executesql procedure. But this should help you understand what’s going on.