Entity Framework: Drop & Create Tables upon Model Change

Technologies: 

• C# (v4.0+)
• Entity Framework 4.3+

Problem:

I am hosting my site on a server where the database itself cannot be dropped for I have limited permissions. However, I am allowed to drop and create tables. So I need a way to use Entity Framework's Code-First approach without dropping the database after model changes.

Solution:

1) Create a new class called  DropCreateDatabaseTables. Use the code below to populate the class code. There should not be any changes needed in order to implement within your solution.

using System;
using System.Data.Entity;
using System.Data.Entity.Infrastructure;
using System.IO;
using System.IO.Compression;
using System.Linq;
using System.Reflection;
using System.Transactions;
using System.Xml;

namespace MySolution.DataAccess.EfSqlServer
{
    public class DropCreateDatabaseTables<TContext> : IDatabaseInitializer<TContext> where TContext : DbContext
    {
        public void InitializeDatabase(TContext context)
        {
            // if the context database exists
            if (context.Database.Exists())
            {
                // if model has changed
                if (!context.Database.CompatibleWithModel(false))
                {
                    // remove all tables
                    this.DropAllTables(context);

                    // create all model tables
                    var dbCreationScript = ((IObjectContextAdapter)context).ObjectContext.CreateDatabaseScript();
                    context.Database.ExecuteSqlCommand(dbCreationScript);

                    // create meta data table
                    this.CreateMetaDataTable(context);

                    // seed initialization data
                    Seed(context);

                    // save
                    context.SaveChanges();
                }
            }
            else
            {
                string dbName = context.Database.Connection.Database;
                string error = String.Format("Database {0} does not exist!", dbName);

                throw new DataMisalignedException(error);
            }
        }

        private void DropAllTables(TContext context)
        {
            // disable all foreign keys
            context.Database.ExecuteSqlCommand("EXEC sp_MSforeachtable @command1 = 'ALTER TABLE ? NOCHECK CONSTRAINT all'");

            bool tryAgain = true;

            // need to perform multiple drop attempts due to the possibility of linked foreign key data
            while (tryAgain)
            {
                try
                {
                    // drop tables
                    context.Database.ExecuteSqlCommand("EXEC sp_MSforeachtable @command1 = 'DROP TABLE ?'");

                    // remove try again flag
                    tryAgain = false;
                }
                catch { } // ignore errors as these are expected due to linked foreign key data
            }
        }

        <summary>
        /// This assumes you are using Entity Framework Code-First 4.3.x or greater.
        /// This uses the __MigrationHistory table NOT the old EdmMetaData table.        
        </summary>
        private void CreateMetaDataTable(TContext context)
        {
            // create meta data table DDL
            string sql = @"CREATE TABLE dbo.__MigrationHistory (
                                MigrationId NVARCHAR(255) NOT NULL,
                                CreatedOn DATETIME NOT NULL,
                                Model VARBINARY(MAX) NOT NULL,
                                ProductVersion NVARCHAR(32) NOT NULL);
 
                            ALTER TABLE dbo.__MigrationHistory ADD PRIMARY KEY (MigrationId);
 
                            INSERT INTO dbo.__MigrationHistory (MigrationId, CreatedOn, Model, ProductVersion)
                            VALUES ('InitialCreate', GetDate(), @p0, @p1);";

            // execute SQL command
            context.Database.ExecuteSqlCommand(sql, GetModel(context), GetProductVersion());
        }

        private byte[] GetModel(TContext context)
        {
            using (var memoryStream = new MemoryStream())
            {
                using (var gzipStream = new GZipStream(memoryStream, CompressionMode.Compress))
                {
                    using (var xmlWriter = XmlWriter.Create(gzipStream, new XmlWriterSettings { Indent = true }))
                    {
                        EdmxWriter.WriteEdmx(context, xmlWriter);
                    }
                }

                return memoryStream.ToArray();
            }
        }

        private string GetProductVersion()
        {
            return typeof(DbContext).Assembly
                                    .GetCustomAttributes(false)
                                    .OfType<AssemblyInformationalVersionAttribute>()
                                    .Single()
                                    .InformationalVersion;
        }

        protected virtual void Seed(TContext context)
        {
            /// Let your Database Initializer class handle the seeding of data
        }
    }
}

2) Next, within your DatabaseInitializer class set it to inherit from DropCreateDatabaseTables. 

    internal class DatabaseInitializer : DropCreateDatabaseTables<DbContext> 
    {
        protected override void Seed(DbContext context)
        {
            base.Seed(context);

            /// TODO: set your seed code here to populate data
        }
    }

That's it! Let me know if you have questions or comments!

MVC: Create Link to Popup jQuery Modal for Partial View

Technologies: 

• C# (v4.0+)
• MVC (v3+)
• Razor
• jQuery (v1.4+)

Problem:

I want a reusable way to create a link to popup a jQuery modal for my partial View. This can be used for editing in a modal instead of a new page, etc.

Solution:

1) Create a  PartialController partial class in the Web project's Controllers folder. Within this partial class create a virtual method called Render. This will be called by the HTML Extension class as shown below.

using System.Web.Mvc;

namespace MySolution.Web.Controllers
{
    public partial class PartialController : Controller
    {
        /// 
 
        /// Render any partial. Passes a null Model. 
        /// 
 
        [AllowAnonymous]
        public virtual ActionResult Render(string path)
        {
            return PartialView(path, null);
        }
    } 
}

2) Create a  HtmlExtensions HTML Helper class in the Web project (if you don't already have one). Within this class create a static method called ActionLinkToModal. This will be called by the View as shown below.

using System;
using System.Web.Mvc;
using System.Web.Mvc.Html;
using System.Web.Routing;

namespace MySolution.Web.Helpers.Html
{
    public static class HtmlExtentions
    {       
        public static MvcHtmlString ActionLinkToModal(this HtmlHelper html, string partialName, string linkText, 
                                                        string cssClass = null, 
                                                        string saveButtonText = "Save", string saveAction = null, 
                                                        string closeButtonText = "Close", bool showCloseButton = true, 
                                                        bool resizable = true, 
                                                        int minWidth = 300, int minHeight = 400, int maxWidth = 900, int maxHeight = 900)
        {
            // declare controller/action link to partial view
            string action = "Render";
            string controller = "Partial";
            string link = String.Format("/{0}/{1}?Path={2}",
                                        controller,
                                        action,
                                        partialName);

            // create onClick jQuery event
            string onClick = String.Format("showModal('{0}', '{1}', '{2}', '{3}', '{4}', {5}, {6}, {7}, {8}, {9}, {10});",
                                            linkText,
                                            link,
                                            saveButtonText,
                                            saveAction,
                                            closeButtonText,
                                            showCloseButton.ToString().ToLower(),
                                            resizable.ToString().ToLower(),
                                            minWidth,
                                            minHeight,
                                            maxWidth,
                                            maxHeight);

            // build the <a> tag
            var anchor = new TagBuilder("a");
            anchor.MergeAttribute("class", cssClass);
            anchor.MergeAttribute("onClick", onClick);
            anchor.MergeAttribute("href", "javascript: void(0);");
            anchor.InnerHtml = linkText;
            string anchorAsHtml = anchor.ToString(TagRenderMode.Normal);

            return MvcHtmlString.Create(anchorAsHtml);
        }
    }
}

3) Create a Javascript method called showModal somewhere in a global JS file. Be sure to include a script reference to the jQuery library (most likely in your HTML <HEAD> section).

function showModal(title, address, saveButtonText, saveAction, closeButtonText, showCloseButton, resizable, minWidth, minHeight, maxWidth, maxHeight) {
    var win = $("<div class='modal'></div>");

    win.dialog({
        title: title,
        modal: true,
        resizable: resizable,
        minWidth: minWidth,
        minHeight: minHeight,
        maxWidth: maxWidth,
        maxHeight: maxHeight,
        open: function () {
            win.load(address);
        }
    });

    var buttons = [];

    if (saveAction != null) {
        var btnSave = { text: saveButtonText, click: function () { window[saveAction](win); } };
        buttons.push(btnSave);
    }

    if (showCloseButton) {
        var btnClose = { text: closeButtonText, click: function () { win.dialog("close"); } };
        buttons.push(btnClose);
    }

    win.dialog("option", "buttons", buttons);
}

4) Now all you have to do is to add the call to the HtmlExtensions class's  ActionLinkToModal method from the View.

   @Html.ActionLinkToModal("_ChangePassword", "Change Password", "link-input", "Save & Close", "mySaveFunc", "Cancel")

5) And notice that I have a SaveAction defined in my View call as mySaveFunc so be sure to create that method in your local Javascript.

    function mySaveFunc(modal) {
        // showing how you can get information you need out of the modal object
        alert(modal.dialog("option", "title"));

        // ... do saving stuff here ... //

        // close modal
        modal.dialog("close");
    }

That's it! Let me know if you have questions or comments!

MVC: Change Site Navigation Link CSS Class for Current Page

Technologies: 

• C# (v4.0+)
• MVC (v3+)
• Razor

Problem:

I want my site navigation link for the current page to have a different CSS class for the current (active) page. This allows the user to easily see which page they are on by looking at the navigation menu.

Solution:

1) Create a  HtmlExtensions HTML Helper class in the Web project (if you don't already have one). Within this class create a static method called ActiveActionLink. This will be called by the View as shown below.

using System;
using System.Web.Mvc;
using System.Web.Mvc.Html;
using System.Web.Routing;

namespace MySolution.Web.Helpers.Html
{
    public static class HtmlExtentions
    {       
        public static MvcHtmlString ActiveActionLink(this HtmlHelper html, string text, string action, string controller, string activeCssClass)
        {
            bool activeItem = false;

            // determine if the given controller/action is the current page
            if (html.ViewContext.RouteData.Values["action"].ToString().Equals(action, StringComparison.CurrentCulture)
                && html.ViewContext.RouteData.Values["controller"].ToString().Equals(controller, StringComparison.CurrentCulture)
            {
                activeItem = true;
            }            
            
            // build the <li> tag
            var li = new TagBuilder("li");
            if (activeItem) li.MergeAttribute("class", activeCssClass);
            li.InnerHtml = html.ActionLink(text, action, controller).ToHtmlString();
            string liAsHtml = li.ToString(TagRenderMode.Normal);
            
            return MvcHtmlString.Create(liAsHtml);
        }      
    }
}

2) Now all you have to do is to add the call to the HtmlExtensions class's ActiveActionLink method from the View.

   

      @Html.ActiveActionLink("Home", "Index", "Home", "current_page_item")
      @Html.ActiveActionLink("Register", "Register", "Security", "current_page_item")
      @Html.ActiveActionLink("Login", "Login", "Security", "current_page_item")
      @Html.ActiveActionLink("Admin", "Index", "Admin", "current_page_item")
   

That's it! Let me know if you have questions or comments!

MVC: How to Secure Site Navigation Links

Technologies: 

• C# (v4.0+)
• MVC (v3+)
• Razor

Problem:

I want to create navigation links for my site, but at the same time secure those links not authorized by certain individuals without proper permissions. I want it to be simple, straightforward and not duplicate my existing security infrastructure efforts.

Solution:

1) First you need to make sure you have tagged all your Controller Methods with the appropriate authorization tag. Below I have previously created my own custom authorize attribute (see post here) called AuthorizeAdminRole. 

using System.Web.Mvc;
using MySolution.Web.Helpers.Security.Authorization;

namespace MySolution.Web.Controllers
{
    public class AdminController : Controller_Base
    {
        [AuthorizeAdminRole]
        public ActionResult Index()
        {
            return View();
        }
    }
}

2) Next, create a  HtmlSecurityExtensions HTML Helper class in the Web project. Within this class create a static method called ShowLinkIfAuthorized. This will be called by the View as show later.

using System;
using System.Globalization;
using System.Web.Mvc;
using System.Web.Mvc.Html;

namespace MySolution.Web.Helpers.Html
{
    public static class HtmlSecurityExtentions
    {       
        public static MvcHtmlString ShowLinkIfAuthorized(this HtmlHelper html, string text, string action, string controller, bool hideIfLoggedIn = false)
        {
            // set default action link (empty)
            MvcHtmlString link = new MvcHtmlString(String.Empty);

            // determine if current user has permission to access controller action
            bool authorized = HasActionPermission(html, action, controller);

            // determine if the current user is logged in (authenticated)
            bool loggedIn = html.ViewContext.HttpContext.User.Identity.IsAuthenticated;

            // if asked to hide if user is logged in AND the user is logged in, then do not authorize this link
            if (hideIfLoggedIn && loggedIn) authorized = false;

            // if authorized
            if (authorized)
            {
                // set the action link
                link = html.ActionLink(text, action, controller);                
            }

            return link;
        }
    }

3) Now to add some extra helper methods within this new HtmlSecurityExtensions class to determine whether the current user has permission to access the controller action. I borrowed this from another post. 

        private static bool HasActionPermission(this HtmlHelper htmlHelper, string actionName, string controllerName)
        {
            ControllerBase controllerToLinkTo = string.IsNullOrEmpty(controllerName)
                ? htmlHelper.ViewContext.Controller
                : GetControllerByName(htmlHelper, controllerName);

            ControllerContext controllerContext = new ControllerContext(htmlHelper.ViewContext.RequestContext, controllerToLinkTo);

            ReflectedControllerDescriptor controllerDescriptor = new ReflectedControllerDescriptor(controllerToLinkTo.GetType());
            ActionDescriptor actionDescriptor = controllerDescriptor.FindAction(controllerContext, actionName);

            return ActionIsAuthorized(controllerContext, actionDescriptor);
        }

        private static bool ActionIsAuthorized(ControllerContext controllerContext, ActionDescriptor actionDescriptor)
        {
            if (actionDescriptor == null)
                return false;

            AuthorizationContext authContext = new AuthorizationContext(controllerContext, actionDescriptor);

            foreach (Filter authFilter in FilterProviders.Providers.GetFilters(authContext, actionDescriptor))
            {
                if (authFilter.Instance is System.Web.Mvc.AuthorizeAttribute)
                {
                    ((IAuthorizationFilter)authFilter.Instance).OnAuthorization(authContext);

                    if (authContext.Result != null)
                        return false;
                }
            }

            return true;
        }

        private static ControllerBase GetControllerByName(HtmlHelper helper, string controllerName)
        {
            IControllerFactory factory = ControllerBuilder.Current.GetControllerFactory();

            IController controller = factory.CreateController(helper.ViewContext.RequestContext, controllerName);

            if (controller == null)
            {
                throw new InvalidOperationException(
                    String.Format(
                        CultureInfo.CurrentUICulture,
                        "Controller factory {0} controller {1} returned null",
                        factory.GetType(),
                        controllerName));
            }

            return (ControllerBase)controller;
        }

4) Finally, the last step is to add the call to the HtmlSecurityExtensions class's ShowLinkIfAuthorized method from the View.

   

@Html.ShowLinkIfAuthorized("Home", "Index", "Home", true)
@Html.ShowLinkIfAuthorized("Register", "Register", "Security", true)
@Html.ShowLinkIfAuthorized("Login", "Login", "Security", true)
@Html.ShowLinkIfAuthorized("Admin", "Index", "Admin")

That's it! Let me know if you have questions or comments!