Hello, I'm getting an error in my Data Service from the following line:
return new Data.sistersDBEntities(new EntityConnection(DataCache.GetCache(STR_BirthdaySister_EF_ConnectionString_Key).ToString()));
Error: DotNetNuke.Modules.SistersBirthdays.Data.sistersDBEntities' does not contain a constructor that takes 1 arguments
Here's my full Data Service (based on Steve Fabians demo)
Background: (dnn7.00.04, VS 2010, IIS7.5) I have one module (works fine) that connects to our SQL server using the same data service code. This second module connects to the same database. Here's the full DS code:
//------------------------------------------------------------------------------
// <copyright file="WebDataService.svc.cs" company="Microsoft">
//     Copyright (c) Microsoft Corporation.  All rights reserved.
// </copyright>
//------------------------------------------------------------------------------
using System;
using System.Collections.Generic;
using System.Data.Services;
using System.Data.Services.Common;
using System.Linq;
using System.ServiceModel.Web;
using System.Web;
using DotNetNuke.Services.Localization;
using System.Data.SqlClient;
using System.Configuration;
using System.Data.EntityClient;
using DotNetNuke.Common.Utilities;

namespace DotNetNuke.Modules.SistersBirthdays.Service
{
    [System.ServiceModel.ServiceBehavior(IncludeExceptionDetailInFaults = true)]
    public class SistersBirthdaysDataService : DataService< Data.sistersDBEntities >
    {
        // This method is called only once to initialize service-wide policies.
        public static void InitializeService(DataServiceConfiguration config)
        {
            config.UseVerboseErrors = true;
            config.SetEntitySetAccessRule("*", EntitySetRights.AllRead);
            config.SetServiceOperationAccessRule("*", ServiceOperationRights.All);
            config.DataServiceBehavior.MaxProtocolVersion = DataServiceProtocolVersion.V3;
        }
        
        protected override Data.sistersDBEntities CreateDataSource()
        {
            return CreateModuleDataSource();
        }

        [WebGet]
        public string GetVersion()
        {
            var ver = System.Reflection.Assembly.GetExecutingAssembly().GetName().Version;
            return String.Format("{0}.{1}.{2}.{3}",
                ver.Major, ver.Minor, ver.Build, ver.Revision);
        }

        [WebGet]
        public string GetResourceString(string key)
        {
            return Localization.GetString(key, "/DesktopModules/BirthdaySister/Views/App_LocalResources/SharedResources.resx");
        }

        private Data.sistersDBEntities CreateModuleDataSource()
        {
            try
            {
                // first check the cache, we only want to do this once
                const string STR_BirthdaySister_EF_ConnectionString_Key = "BirthdaySister_EF_ConnectionString_Key";

                //if (DataCache.GetCache(STR_BirthdaySister_EF_ConnectionString_Key) == null)
                //{
                // if not in the cache, construct the entity connection and cache it
                using (var SiteSQLConnection = new SqlConnection(
                    ConfigurationManager.ConnectionStrings["sistersDBEntities"].ConnectionString))
                {
                    //check if the connection string has integrated security enabled
                    {
                        bool isIntergratedEnabled = SiteSQLConnection.ConnectionString.Contains("Integrated Security");

                        //Build the Entity Framework connection string from the derived settings
                        var NewSQLConnectionString = new SqlConnectionStringBuilder();
                        var _with1 = NewSQLConnectionString;
                        _with1.DataSource = SiteSQLConnection.DataSource;
                        _with1.InitialCatalog = SiteSQLConnection.Database;
                        if (!isIntergratedEnabled)
                        {
                            string _uid, _pwd = string.Empty;
                            GetUserCredentialsFromConfigFile(SiteSQLConnection.ConnectionString, out _uid, out _pwd);
                            _with1.UserID = _uid;
                            _with1.Password = _pwd;
                        }
                        else
                        {
                            _with1.IntegratedSecurity = isIntergratedEnabled;
                            //.UserInstance = True
                        }
                        _with1.MultipleActiveResultSets = true;

                        var EFConnectionStringBuilder = new EntityConnectionStringBuilder();
                        var _with2 = EFConnectionStringBuilder;
                        _with2.Provider = "System.Data.SqlClient";
                        _with2.ProviderConnectionString = NewSQLConnectionString.ToString();
                        _with2.Metadata = "res://*/Data.SistersBirthdayModel.csdl|res://*/Data.SistersBirthdayModel.ssdl|res://*/Data.SistersBirthdayModel.msl";

                        DataCache.SetCache(STR_BirthdaySister_EF_ConnectionString_Key, EFConnectionStringBuilder.ToString());
                    }

                }
                //}

                // now establish the connection from the cache
                return new Data.sistersDBEntities(new EntityConnection(DataCache.GetCache(STR_BirthdaySister_EF_ConnectionString_Key).ToString()));
            }
            catch (Exception e)
            {
                throw new Exception(e.Message);
            }

        }

        private static void GetUserCredentialsFromConfigFile(string strConn, out string userid, out string password)
        {
            var s = new SqlConnectionStringBuilder(strConn);
            userid = s.UserID;
            password = s.Password;
            return;
        }
    }
}

I don't know what your problem is but I doubt that is it.  I have multiple modules, same page, all connecting to the same DB. No problem.