Query fast in SSMS but slow/wont run in C# application

Question

I know there are quite a few other posts and articles on this but I have been searching for a solution hours now and nothing has worked for me. I have a query that generates a listing of all SQL Reporting Services (SSRS) reports listed on a given server with their associated parameters and valid values:

;WITH XMLNAMESPACES (
DEFAULT 'http://schemas.microsoft.com/sqlserver/reporting/2008/01/reportdefinition',
'http://schemas.microsoft.com/SQLServer/reporting/reportdesigner' AS rd --ReportDefinition
)
SELECT 
   NAME as Name
   , PATH as Path
   , x.value ('@Name', 'VARCHAR(100)') AS ReportParameterName
   , x.value ('DataType[1]', 'VARCHAR(100)') AS DataType
   , x.value ('AllowBlank[1]', 'VARCHAR(50)') AS AllowBlank
   , x.value ('Prompt[1]', 'VARCHAR(100)') AS Prompt
   , x.value ('Hidden[1]', 'VARCHAR(100)') AS Hidden
   , x.value ('data(DefaultValue/Values/Value)[1]', 'VARCHAR(100)') AS DefaultValue
   , y.value ('Value[1]','VARCHAR(100)') AS VaildValues
   , y.value ('Label[1]','VARCHAR(100)') AS VaildValuesLabel
FROM (
   SELECT  PATH
           , NAME
           , CAST(CAST(content AS VARBINARY(MAX)) AS XML) AS ReportXML 
   FROM Catalog 
   WHERE CONTENT IS NOT NULL AND TYPE = 2
   ) A
CROSS APPLY ReportXML.nodes('/Report/ReportParameters/ReportParameter') R(x)
OUTER APPLY R.x.nodes('ValidValues/ParameterValues/ParameterValue') P(y) 
ORDER BY NAME

This query takes about 4 and a half minutes to run in SSMS. I want to take the results of this query in the form of a C# DataTable, to use as the parameter for a stored procedure that runs on a different server. Unfortunately when running the SQL script through my C# code the takes at least 3 hours to run, assuming it would ever finish at all (gave up after 3 hours).

I know the SET options are different when running from SSMS and from application so, I tried to manually make the settings the same as they are in SSMS. Here is a snippet of the code:

DataSet ds = new DataSet();
string SQL_Script = File.ReadAllText(runRdlQueryFilePath);
using (SqlConnection conn = new SqlConnection(sqlConnectionString))
        {

            SqlDataAdapter da = new SqlDataAdapter();
            SqlCommand cmd = conn.CreateCommand();
            cmd.CommandText = SQL_Script;
            da.SelectCommand = cmd;
            conn.Open();
            Console.WriteLine("setting QUOTED_IDENTIFIER on...");
            using (SqlCommand comm = new SqlCommand("SET QUOTED_IDENTIFIER ON", conn))
            {
                comm.ExecuteNonQuery();
            }
            Console.WriteLine("setting ANSI_NULLS on...");
            using (SqlCommand comm = new SqlCommand("SET ANSI_NULLS ON", conn))
            {
                comm.ExecuteNonQuery();
            }
            Console.WriteLine("setting ARITHABORT on...");
            using (SqlCommand comm = new SqlCommand("SET ARITHABORT ON", conn))
            {
                comm.ExecuteNonQuery();
            }
            //this one will not run for some reason but I think it is the default when running from C# client anyways
            //using (SqlCommand comm = new SqlCommand("SET CONCAT_NULL_YEILDS_NULL ON", conn))
            //{
            //    comm.ExecuteNonQuery();
            //}
            Console.WriteLine("setting  XACT_ABORT on...");
            using (SqlCommand comm = new SqlCommand("SET XACT_ABORT ON", conn))
            {
                comm.ExecuteNonQuery();
            }
            Console.WriteLine("setting LOCK_TIMEOUT -1...");
            using (SqlCommand comm = new SqlCommand("SET LOCK_TIMEOUT -1", conn))
            {
                comm.ExecuteNonQuery();
            }
            Console.WriteLine("Executing get rdl info query, this may take some time..."); 

            da.Fill(ds);

            //I have also tried this method of filling the DataSet...
            /*
            Server server = new Server(new ServerConnection(conn));
                //bool queryRan = true;
                //read sql file
                string script = File.ReadAllText(runRdlQueryFilePath);
            Console.WriteLine("Executing get rdl info query, this may take some time...");
            ds = server.ConnectionContext.ExecuteWithResults(script);
            */
        }

I don't see how parameter sniffing would be an issue here as the query takes no parameters, but I tried putting an

OPTION (RECOMPILE)

on my query just for fun and had no success with this either. Unfortunately I am not the owner of this database and do not have permissions to create a stored procedure on it, so I have not tried converting the query to a stored procedure.

Any ideas what else could be stopping the query from executing efficiently in the application?

Thanks for any help!