Kendo MVC Grid DataSourceRequest with AutoMapper

Kendo Grid does not work directly with AutoMapper but could be managed by simple trick using mapping through ToDataSourceResult. The solution works fine until different filters are applied.

The problems occurs because passed filters refer to view model properties where as database model properties are required after AutoMapper is implemented.

So, the plan is to intercept DataSourceRequest  and modify names based on database model. To do that we are going to create implementation of CustomModelBinderAttribute to catch calls and have our own implementation of DataSourceRequestAttribute from Kendo MVC. I will be using same source code from Kendo but will replace column names for different criteria for sort, filters, group etc.

Let's first look into how that will be implemented.

     public ActionResult GetRoles([MyDataSourceRequest(GridId.RolesUserGrid)] DataSourceRequest request)  
     {  
       if (request == null)  
       {  
         throw new ArgumentNullException("request");  
       }  
       return Json(UnitOfWork.RoleRepository.All()  // DB Call
         .ToDataSourceResult(request, data => Mapper.Map<RoleViewModel>(data)), JsonRequestBehavior.AllowGet);  
     }  

As per above example it looks pretty simple to implement. The whole logic and idea is hidden under MyDataSourceRequest and GridId enum. MyDataSourceRequest is a direct implementation of original DataSourceRequest from Kendo MVC but with column name changes.

To know which database model is mapped to which view model. We will have enum for all AJAX grid calls and then through that we will be able to know mapped view model.

KendoHelper.cs

   /// <summary>  
     /// Grid Ids  
     /// </summary>  
     public enum GridId  
     {  
       /// <summary>  
       /// The roles user grid  
       /// </summary>  
       RolesUserGrid,  
     }  
     /// <summary>  
     /// Gets the type of the grid's AutoMapper class.  
     /// </summary>  
     /// <param name="gridId">The grid identifier.</param>  
     /// <returns></returns>  
     public static Type GetGridAutoMapperType(this GridId gridId)  
     {  
       switch (gridId)  
       {  
         case GridId.RolesUserGrid:  
           return typeof(RoleViewModel);  
       }  
       return null;  
     }  

The GetGridAutoMapperType is giving us type for the mapped class. Through this we know that GridId.RolesUserGrid is mapped to RoleViewModel class.

This is the minimum thing required to know the mapping. Now, we need two more things, the original property names by passing view model type from GetGridAutoMapperType and another function to replace view model property names with database model property names.

KendoHelper.cs

 /// <summary>  
     /// Gets the mapped property names from AutoMapper configuration.  
     /// </summary>  
     /// <param name="autoMapperType">Type of the automatic mapper.</param>  
     /// <returns></returns>  
     /// <exception cref="System.ArgumentNullException"><T>;Unable to find given type in AutoMapper.</exception>  
     public static IDictionary<string, string> GetMappedNames(Type autoMapperType)  
     {  
       if (autoMapperType == null)  
       {  
         return null;  
       }  
       var mainItem = Mapper.GetAllTypeMaps().SingleOrDefault(m => m.DestinationType.Equals(autoMapperType));  
       if (mainItem == null)  
       {  
         throw new ArgumentNullException("<T>", "Unable to find given type in AutoMapper.");  
       }  
       return (from prop in mainItem.GetPropertyMaps()  
           where prop != null &&  
           prop.DestinationProperty != null &&  
           prop.SourceMember != null &&  
           prop.DestinationProperty.Name != prop.SourceMember.Name  
           let sourceName = Convert.ToString(prop.CustomExpression.Body)  
           select new  
           {  
             DestinationPropertyName = prop.DestinationProperty.Name,  
             SourceMemberName = (sourceName != null ? sourceName.Remove(0, String.Join(String.Empty,  
             prop.CustomExpression.Parameters.Select(p => p.Name)).Length + 1) : prop.SourceMember.Name)  
           }).ToDictionary(prop => prop.DestinationPropertyName, prop => prop.SourceMemberName);  
     }  
     /// <summary>  
     /// Gets the name of the mapped property.  
     /// </summary>  
     /// <param name="value">The value.</param>  
     /// <param name="mappedProperties">The mapped properties.</param>  
     /// <param name="isReverse">if set to <c>true</c> reverse mapping.</param>  
     /// <returns>Mapped property for given value</returns>  
     public static string GetMappedName(this string value, IDictionary<string, string> mappedProperties,  
       bool isReverse = false)  
     {  
       if (String.IsNullOrEmpty(value) ||  
         mappedProperties == null || mappedProperties.Count == 0)  
       {  
         return value;  
       }  
       var mappedPropertyValue = value;  
       foreach (var mappedproperty in mappedProperties)  
       {  
         var dicKey = isReverse ? mappedproperty.Value : mappedproperty.Key;  
         var dicValue = isReverse ? mappedproperty.Key : mappedproperty.Value;  
         var regex = new Regex(String.Format(@"\b{0}\b", dicKey));  
         if (regex.IsMatch(dicKey))  
         {  
           mappedPropertyValue = regex.Replace(mappedPropertyValue, dicValue);  
         }  
       }  
       return mappedPropertyValue;  
     }  

With GetMappedNames function we can get properties names from database model and view model. The GetMappedName helper method would help us to replace string on model.

These are all helper methods we need, we can start creating attribute and own implementation of DataSourceRequest.

MyDataSourceRequestAttribute.cs

 /// <summary>  
   /// Custom data source request attribute  
   /// </summary>  
   public class MyDataSourceRequestAttribute  
     : CustomModelBinderAttribute  
   {  
     /// <summary>  
     /// Gets or sets the prefix.  
     /// </summary>  
     /// <value>  
     /// The prefix.  
     /// </value>  
     public string Prefix { get; set; }  
     /// <summary>  
     /// Gets or sets the grid identifier.  
     /// </summary>  
     /// <value>  
     /// The grid identifier.  
     /// </value>  
     public GridId? GridUniqueId { get; set; }  
     /// <summary>  
     /// Initializes a new instance of the <see cref="MyDataSourceRequestAttribute"/> class.  
     /// </summary>  
     public MyDataSourceRequestAttribute()  
     {  
     }  
     /// <summary>  
     /// Initializes a new instance of the <see cref="MyDataSourceRequestAttribute"/> class.  
     /// </summary>  
     /// <param name="gridId">The grid identifier.</param>  
     public MyDataSourceRequestAttribute(GridId gridId)  
     {  
       GridUniqueId = gridId;  
     }  
     /// <summary>  
     /// Retrieves the associated model binder.  
     /// </summary>  
     /// <returns>  
     /// A reference to an object that implements the <see cref="T:System.Web.Mvc.IModelBinder" /> interface.  
     /// </returns>  
     public override IModelBinder GetBinder()  
     {  
       var dataSourceRequestModelBinder = new MyDataSourceRequestModelBinder(GridUniqueId);  
       dataSourceRequestModelBinder.Prefix = this.Prefix;  
       return dataSourceRequestModelBinder;  
     }  
   }  

The above attribute is pretty simple takes GridId and pass it to MyDataSourceRequestModelBinder. This is the model binder which will consume our helper classes and replace property names.

MyDataSourceRequestModelBinder.cs

   /// <summary>  
   /// Custom DataSourceRequestModelBinder to handle AutoMapper mappings  
   /// </summary>  
   public class MyDataSourceRequestModelBinder  
     : IModelBinder  
   {  
     /// <summary>  
     /// Initializes a new instance of the <see cref="MyDataSourceRequestModelBinder"/> class.  
     /// </summary>  
     /// <param name="gridId">The grid identifier.</param>  
     public MyDataSourceRequestModelBinder(GridId? gridId)  
     {  
       GridUniqueId = gridId;  
     }  
     /// <summary>  
     /// Gets or sets the prefix.  
     /// </summary>  
     /// <value>  
     /// The prefix.  
     /// </value>  
     public string Prefix { get; set; }  
     /// <summary>  
     /// Gets or sets the grid identifier.  
     /// </summary>  
     /// <value>  
     /// The grid identifier.  
     /// </value>  
     public GridId? GridUniqueId { get; set; }  
     /// <summary>  
     /// Gets or sets the mapped properties.  
     /// </summary>  
     /// <value>  
     /// The mapped properties.  
     /// </value>  
     private IDictionary<string, string> MappedProperties { get; set; }  
     /// <summary>  
     /// Binds the model to a value by using the specified controller context and binding context.  
     /// </summary>  
     /// <param name="controllerContext">The controller context.</param>  
     /// <param name="bindingContext">The binding context.</param>  
     /// <returns>  
     /// The bound value.  
     /// </returns>  
     public object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)  
     {  
       if (!GridUniqueId.HasValue)  
       {  
         DataSourceRequestModelBinder kendoDataRequestBinder = new DataSourceRequestModelBinder();  
         return kendoDataRequestBinder.BindModel(controllerContext, bindingContext);  
       }  
       MappedProperties = GridUniqueId.Value.GetMappedPropertyNames();  
       string sorts;  
       string groups;  
       string filters;  
       string aggregates;  
       int pageIndex;  
       int pageSize;  
       DataSourceRequest dataSourceRequest = new DataSourceRequest();  
       if (this.TryGetValue<string>(bindingContext, GridUrlParameters.Sort, out sorts))  
       {  
         dataSourceRequest.Sorts = GridDescriptorSerializer.  
           Deserialize<SortDescriptor>(sorts.GetMappedName(MappedProperties));  
       }  
       if (this.TryGetValue<int>(bindingContext, GridUrlParameters.Page, out pageIndex))  
       {  
         dataSourceRequest.Page = pageIndex;  
       }  
       if (this.TryGetValue<int>(bindingContext, GridUrlParameters.PageSize, out pageSize))  
       {  
         dataSourceRequest.PageSize = pageSize;  
       }  
       if (this.TryGetValue<string>(bindingContext, GridUrlParameters.Filter, out filters))  
       {  
         dataSourceRequest.Filters = FilterDescriptorFactory.Create(filters.GetMappedName(MappedProperties));  
       }  
       if (this.TryGetValue<string>(bindingContext, GridUrlParameters.Group, out groups))  
       {  
         dataSourceRequest.Groups = GridDescriptorSerializer.  
           Deserialize<GroupDescriptor>(groups.GetMappedName(MappedProperties));  
       }  
       if (this.TryGetValue<string>(bindingContext, GridUrlParameters.Aggregates, out aggregates))  
       {  
         dataSourceRequest.Aggregates = GridDescriptorSerializer.  
           Deserialize<AggregateDescriptor>(aggregates.GetMappedName(MappedProperties));  
       }  
       return dataSourceRequest;  
     }  
     /// <summary>  
     /// Tries to get the value and typecast.  
     /// </summary>  
     /// <typeparam name="T"></typeparam>  
     /// <param name="bindingContext">The binding context.</param>  
     /// <param name="key">The key.</param>  
     /// <param name="result">The result.</param>  
     /// <returns>Typecasted value</returns>  
     private bool TryGetValue<T>(ModelBindingContext bindingContext, string key, out T result)  
     {  
       if (this.Prefix.HasValue())  
       {  
         key = string.Concat(this.Prefix, "-", key);  
       }  
       ValueProviderResult value = bindingContext.ValueProvider.GetValue(key);  
       if (value == null)  
       {  
         result = default(T);  
         return false;  
       }  
       result = (T)value.ConvertTo(typeof(T));  
       return true;  
     }  
   }  

The entire source code of MyDataSourceRequestModelBinder is taken from original Kendo MVC binder. The only part that has been modified is for replacing property names by using created helper methods GridUniqueId.Value.GetMappedPropertyNames() and GetMappedName(MappedProperties) to restore it to correct value.

NOTE: This is compatible with Storing and restoring Kendo Grid state from Database. Just we need to implement described approach in it.

Update: AutoMapper Linq Projection implementation for avoiding getting all tuples from row.