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Correcting errors with System.Net.DnsPermission using C#?


I am creating a C# CLR Function for SQL Server 2008 (just for background).

I am not having difficulties with the SQL Server at all, so I am not asking any questions regarding SQL Server. I am getting the following error:

A .NET Framework error occurred during execution of user-defined routine or aggregate "Function1":
System.Security.SecurityException: Request for the permission of type 'System.Net.DnsPermission, System, Version=, Culture=neutral, PublicKeyToken=b77a5c561934e089' failed.
   at System.Security.CodeAccessSecurityEngine.Check(Object demand, StackCrawlMark& stackMark, Boolean isPermSet)
   at System.Security.CodeAccessPermission.Demand()
   at System.Net.Dns.GetHostEntry(String hostNameOrAddress)
   at UserDefinedFunctions.Function1(String ipaddress)

I have attached the code that generated this error. I have not used .Net before and I would like to know how to resolve this permission error.

Some background:

I have attempted to find the .Net MMC on my Win2K8 r2 server and I am unable to locate it.
I have added the application server role to the server.
I have successfully deployed working CLR applications to this server.
I have attempted to install the 3.5.1 framework, and it says that it is already installed and that I would need to use Server Manager in order to add or remove it.

Thanks in advance for your help.

using System;
using System.Net;
using System.Security.Permissions;
using System.Data;
using System.Data.SqlClient;
using System.Data.SqlTypes;
using Microsoft.SqlServer.Server;

public partial class UserDefinedFunctions
    public static SqlString Function1(string ipaddress)
        // check string len
        if (ipaddress.Length < 7) return new SqlString("Unknown");
        // attempt a lookup
            // set 
            IPHostEntry ipEntry; // holds entry to lookup
            // request permission for dns lookup
            DnsPermission perm = new DnsPermission(PermissionState.Unrestricted);
            // attempt to resolve
            ipEntry = Dns.GetHostEntry(ipaddress);
            // catch data and return
            return new SqlString(ipEntry.HostName);
        catch (System.Net.Sockets.SocketException se) {return new SqlString("Unknown");}
        catch (System.FormatException fe) {return new SqlString("Unknown");}

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Avatar of Rimvis
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You should mark your database as trustworthy.

Open SSMS, and execute this:

ALTER DATABASE <your db name goes here> SET TRUSTWORTHY ON
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I followed your instructions and I still get the same error.
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Thank you so much. This worked correctly!