T4 For Generating POCOs Over LLBLGen Pro Entities?

Question

As I understand it, LLBLGen Pro cannot generate POCOs over it's own entities (see here: http://www.llblgen.com/Pages/featuresLLBLGenPro.aspx).

Has anyone written a T4 that will generate POCO classes corresponding to LLBLGen Pro entities and generate the appropriate transformation logic to go to and from an entity and POCO? Has anyone else come up with a solution that doesn't involve manually writing tons of transformation code?

Answer 1

We generated DTOs from LLBLGen rather than using T4.

We had a need to create DTOs from an Entity. These aren't technically POCOs because they have a ToEntity() and FromEntity() method, but perhaps this will work for you.

We created an IDTO<T> interface that was then implemented by the DTO classes (one for each entity). Rather than modifying the entity templates, we added DTOExtension methods that would convert an Entity to a DTO (as well as numerous other helper conversions).

Here are the template files you can use within LLBLGen v2.6. The template designer in version 3 is much easier to use, and you can convert much of this code for version 3 if you need to.

File: entityDTOInterface.template

using System;
using System.ComponentModel;
using System.Collections;
using System.Runtime.Serialization;

using <[RootNamespace]>.HelperClasses;
using <[RootNamespace]>.EntityClasses;

using SD.LLBLGen.Pro.ORMSupportClasses;

namespace <[RootNamespace]>.DTOClasses
{
    /// <summary>
    /// DTO interface.
    /// </summary>
    public interface IDTO<T>
    {
        T ToEntity(T toFill);
        IDTO<T> FromEntity(T entityInstance, Hashtable seenObjects, Hashtable parents);
    }
}

File: entityDTO.template

using System;
using System.ComponentModel;
using System.Collections;
using System.Runtime.Serialization;

using <[RootNamespace]>.HelperClasses;
using <[RootNamespace]>.EntityClasses;

using SD.LLBLGen.Pro.ORMSupportClasses;

namespace <[RootNamespace]>.DTOClasses
{
    <[ UserCodeRegion "AdditionalNamespaces" ]>
    // __LLBLGENPRO_USER_CODE_REGION_START AdditionalNamespaces
    // __LLBLGENPRO_USER_CODE_REGION_END
    <[ EndUserCodeRegion ]> 
    /// <summary>
    /// DTO class for the entity '<[CurrentEntityName]>'.
    /// </summary>
    [Serializable]
    public <[If UsePartialClasses]>partial <[EndIf]>class <[CurrentEntityName]>DTO : <[ If IsSubType ]><[ SuperTypeName ]>DTO, <[ EndIf]>IDTO<<[CurrentEntityName]>Entity><[ UserCodeRegion "AdditionalInterfaces" ]>
        // __LLBLGENPRO_USER_CODE_REGION_START AdditionalInterfaces
        // __LLBLGENPRO_USER_CODE_REGION_END
        <[ EndUserCodeRegion ]> 
    {
        #region Entity Field Public Properties

<[Foreach EntityField CrLf]>        /// <summary>Get or set the <[EntityFieldName]> property that maps to the Entity <[CurrentEntityName]></summary>
        public virtual <[If GenerateAsNullableType]><[TypeOfField]>?<[Else]><[TypeOfField]><[EndIf]> <[EntityFieldName]> { get; set; }
<[NextForeach]>        
        #endregion

        #region Related Field Public Properties

<[ Foreach RelatedEntityField CrLf]>        /// <summary>Get or set the <[MappedFieldNameRelatedField]> property that maps to the Entity <[CurrentEntityName]>'s <[ MappedFieldNameRelation ]>.<[ RelatedEntityFieldName ]></summary>
        public virtual <[If GenerateAsNullableType]><[TypeOfField]>?<[Else]><[TypeOfField]><[EndIf]> <[ MappedFieldNameRelatedField ]> { get; private set; }<[NextForeach]>

        #endregion

        #region Custom Fields
        <[ UserCodeRegion "CustomFieldCode" ]>
        // __LLBLGENPRO_USER_CODE_REGION_START CustomFieldCode
        // __LLBLGENPRO_USER_CODE_REGION_END
        <[ EndUserCodeRegion ]>
        #endregion

        #region Ctors

        /// <summary>
        /// CTor
        /// </summary>
        public <[CurrentEntityName]>DTO()
        {        
        }

        /// <summary>
        /// CTor which initializes the DTO with values from its corresponding entity
        /// </summary>
        /// <param name="entityInstance">The entity instance which holds the values for this DTO</param>
        public <[CurrentEntityName]>DTO(<[CurrentEntityName]>Entity entityInstance) : this(entityInstance, new Hashtable(), new Hashtable()) { }

        internal <[CurrentEntityName]>DTO(<[CurrentEntityName]>Entity entityInstance, Hashtable seenObjects, Hashtable parents)<[ If IsSubType ]> : base(entityInstance, seenObjects, parents)<[ EndIf]>
        {
            FromEntity(entityInstance, seenObjects, parents);
        }

        #endregion

        /// <summary>
        /// Creates a <[CurrentEntityName]>DTO object from the given entity.
        /// </summary>
        public virtual IDTO<<[CurrentEntityName]>Entity> FromEntity(<[CurrentEntityName]>Entity entityInstance, Hashtable seenObjects, Hashtable parents)
        {
            <[ If IsSubType ]>base.FromEntity(entityInstance, seenObjects, parents);
            <[ EndIf]>seenObjects[entityInstance] = this;
            parents = new Hashtable(parents);
            parents.Add(entityInstance, null);

<[Foreach EntityField CrLf]>            this.<[EntityFieldName]> = entityInstance.<[EntityFieldName]>;<[NextForeach]>
<[Foreach RelatedEntityField CrLf]>            if (entityInstance.AlreadyFetched<[MappedFieldNameRelation]>)
                this.<[MappedFieldNameRelatedField]> = entityInstance.<[MappedFieldNameRelatedField]>;<[NextForeach]>
<[Foreach RelatedEntity OneToMany CrLf]><[If Not MappedFieldRelationIsHidden]>            if (entityInstance.AlreadyFetched<[MappedFieldNameRelation]>)
                <[MappedFieldNameRelation]> = RelatedArray<<[RelatedEntityName]>DTO, <[RelatedEntityName]>Entity>(entityInstance.<[MappedFieldNameRelation]>, seenObjects, parents);<[EndIf]><[NextForeach]>
<[Foreach RelatedEntity ManyToMany CrLf]><[If Not MappedFieldRelationIsHidden]>            if (entityInstance.AlreadyFetched<[MappedFieldNameRelation]>)
                <[MappedFieldNameRelation]> = RelatedArray<<[RelatedEntityName]>DTO, <[RelatedEntityName]>Entity>(entityInstance.<[MappedFieldNameRelation]>, seenObjects, parents);<[EndIf]><[NextForeach]>
<[Foreach RelatedEntity ManyToOne CrLf]><[If Not MappedFieldRelationIsHidden]>            if (entityInstance.AlreadyFetched<[MappedFieldNameRelation]>)
                <[MappedFieldNameRelation]> = RelatedObject<<[RelatedEntityName]>DTO, <[RelatedEntityName]>Entity>(entityInstance.<[MappedFieldNameRelation]>, seenObjects, parents);//(new <[RelatedEntityName]>DTO(entityInstance.<[MappedFieldNameRelation]>, seenObjects);<[EndIf]><[NextForeach]>
<[Foreach RelatedEntity OneToOne CrLf]><[If Not MappedFieldRelationIsHidden]>            if (entityInstance.AlreadyFetched<[MappedFieldNameRelation]>)
                <[MappedFieldNameRelation]> = RelatedObject<<[RelatedEntityName]>DTO, <[RelatedEntityName]>Entity>(entityInstance.<[MappedFieldNameRelation]>, seenObjects, parents);<[EndIf]><[NextForeach]>

            return this;
        }

        <[ If Not IsSubType ]>
        /// <summary>
        /// Get a collection of DTO objects created from entities related to <[CurrentEntityName]>Entity.
        /// It keeps track of entities previously seen to prevent an infinite loop.
        /// <summary>
        protected virtual T[] RelatedArray<T,U>(EntityCollectionBase<U> entities, Hashtable seenObjects, Hashtable parents) where T : class, IDTO<U>, new() where U : EntityBase
        {
            if (null == entities)
            {
                    return null;
            }

            T[] arr = new T[entities.Count];
            int i = 0;

            foreach (U entity in entities)
            {
                if (parents.Contains(entity))
                {
                    return null;
                }
            }

            foreach (U entity in entities)
            {
                if (seenObjects.Contains(entity))
                {
                    arr[i++] = seenObjects[entity] as T;
                }
                else
                {
                    arr[i++] = new T().FromEntity(entity, seenObjects, parents) as T;
                }
            }
            return arr;
        }

        /// <summary>
        /// Creates a DTO object from the given related <[CurrentEntityName]>Entity entity.
        /// This is used to populate a single DTO from a single relation of the <[CurrentEntityName]>Entity.
        /// <summary>
        protected virtual T RelatedObject<T,U>(U entityInstance, Hashtable seenObjects, Hashtable parents) where T : class, IDTO<U>, new() where U : EntityBase
        {
            if (null == entityInstance)
            {
                return null;
            }

            if (seenObjects.Contains(entityInstance))
            {
                if (parents.Contains(entityInstance))
                {
                    return null;
                }
                else
                {
                    return seenObjects[entityInstance] as T;
                }
            }

            return new T().FromEntity(entityInstance, seenObjects, parents) as T;
        }

        <[ EndIf]>
        /// <summary>
        /// Get a collection of individual DTO objects from the EntityCollectionBase<<[CurrentEntityName]>Entity> collection.
        /// <summary>
        public static <[CurrentEntityName]>DTO[] ToDTOArray(EntityCollectionBase<<[CurrentEntityName]>Entity> entities)
        {
            Hashtable seenObjects = new Hashtable();
            <[CurrentEntityName]>DTO[] arr = new <[CurrentEntityName]>DTO[entities.Count];
            for (int i = 0; i < entities.Count; i++)
            {
                arr[i] = new <[CurrentEntityName]>DTO().FromEntity(entities[i], seenObjects, new Hashtable()) as <[CurrentEntityName]>DTO;
            }
            return arr;
        }

        /// <summary>
        /// Creates a new entity instance and copies over the values of this DTO
        /// </summary>
        public <[ If IsSubType ]>override <[SuperTypeName]><[ Else]>virtual <[CurrentEntityName]><[ EndIf]>Entity ToEntity()
        {
            return ToEntity(new <[CurrentEntityName]>Entity());
        }

        /// <summary>
        /// Copies over the values of this DTO into the entity passed in. 
        /// Readonly fields on the entity are NOT copied to the entity from this DTO.
        /// </summary>
        public virtual <[CurrentEntityName]>Entity ToEntity(<[CurrentEntityName]>Entity toFill)
        {
<[Foreach EntityField CrLf]><[If IsReadOnly ]><[ Else ]>            toFill.<[EntityFieldName]> = this.<[EntityFieldName]>;<[ EndIf ]><[NextForeach]>

<[ If IsSubType ]>            base.ToEntity(toFill);<[ EndIf]>        
            return toFill;
        }

        #region Relation Fields

<[Foreach RelatedEntity OneToMany CrLf]><[If Not MappedFieldRelationIsHidden]>
        /// <summary> Gets the EntityCollectionBase with the related entities of type '<[RelatedEntityName]>Entity' which are related to this entity via a relation of type '1:n'.
        /// If the EntityCollectionBase hasn't been fetched yet, the collection returned will be empty.</summary>
        public virtual <[RelatedEntityName]>DTO[] <[MappedFieldNameRelation]> { get; set; }<[EndIf]><[NextForeach]>
<[Foreach RelatedEntity ManyToMany CrLf]><[If Not MappedFieldRelationIsHidden]>
        /// <summary> Gets the EntityCollectionBase with the related entities of type '<[RelatedEntityName]>Entity' which are related to this entity via a relation of type 'm:n'.
        /// If the EntityCollectionBase hasn't been fetched yet, the collection returned will be empty.</summary>
        public virtual <[RelatedEntityName]>DTO[] <[MappedFieldNameRelation]> { get; set; }<[EndIf]><[NextForeach]>
<[Foreach RelatedEntity ManyToOne CrLf]><[If Not MappedFieldRelationIsHidden]>
        /// <summary> Gets / sets related entity of type '<[RelatedEntityName]>Entity' which has to be set using a fetch action earlier. If no related entity
        /// is set for this property, null is returned. This property is not visible in databound grids.</summary>
        [Browsable(false)]
        public virtual <[RelatedEntityName]>DTO <[MappedFieldNameRelation]> { get; set; }<[EndIf]><[NextForeach]>
<[Foreach RelatedEntity OneToOne CrLf]><[If Not MappedFieldRelationIsHidden]>
        /// <summary> Gets / sets related entity of type '<[RelatedEntityName]>Entity' which has to be set using a fetch action earlier. If no related entity
        /// is set for this property, null is returned. This property is not visible in databound grids.</summary>
        [Browsable(false)]
        public virtual <[RelatedEntityName]>DTO <[MappedFieldNameRelation]> { get; set; }<[EndIf]><[NextForeach]>

        #endregion

        #region Custom DTO code
        <[ UserCodeRegion "CustomDTOCode" ]>
        // __LLBLGENPRO_USER_CODE_REGION_START CustomDTOCode
        // __LLBLGENPRO_USER_CODE_REGION_END
        <[ EndUserCodeRegion ]>
        #endregion
    }
}

File: dtoExtensions.template

using System;
using System.Collections.Generic;
using System.Linq;
using <[RootNamespace]>;
using <[RootNamespace]>.EntityClasses;
using <[RootNamespace]>.CollectionClasses;
using <[RootNamespace]>.DTOClasses;
using <[RootNamespace]>.HelperClasses;

namespace <[RootNamespace]>.DTOClasses
{
    /// <summary>
    /// Generates extension methods for converting Entities to DTOs
    /// This class is generated. Do not modify.
    /// </summary>
    public static <[If UsePartialClasses]>partial <[EndIf]>class Extensions
    {
<[If HasEntity]><[Foreach Entity]>
        /// <summary>Create a <[CurrentEntityName]> DTO from a <[CurrentEntityName]> entity</summary>
        /// <returns>The DTO created</returns>
        public static <[CurrentEntityName]>DTO ToDTO(this <[CurrentEntityName]>Entity entity)
        {
            <[CurrentEntityName]>DTO dto = null;
            if (entity != null)
                dto = new <[CurrentEntityName]>DTO(entity);
            return dto;
        }

        /// <summary>Create a list of <[CurrentEntityName]>DTO from a <[CurrentEntityName]>Collection</summary>
        /// <returns>The DTO list created</returns>
        public static List<<[CurrentEntityName]>DTO> ToDTOs(this <[CurrentEntityName]>Collection collection)
        {
            List<<[CurrentEntityName]>DTO> dtoList = new List<<[CurrentEntityName]>DTO>(collection.Count);
            foreach(<[CurrentEntityName]>Entity entity in collection)
                dtoList.Add(new <[CurrentEntityName]>DTO(entity));
            return dtoList;
        }

        /// <summary>Create a list of <[CurrentEntityName]>DTO from a List of <[CurrentEntityName]> entities</summary>
        /// <returns>The DTO list created</returns>
        public static List<<[CurrentEntityName]>DTO> ToDTOs(this List<<[CurrentEntityName]>Entity> entities)
        {
            return entities.ConvertAll<<[CurrentEntityName]>DTO>(e => new <[CurrentEntityName]>DTO(e));
        }

        /// <summary>From the queryable object, get a list of <[CurrentEntityName]>DTO</summary>
        /// <returns>The DTO list created</returns>
        public static List<<[CurrentEntityName]>DTO> ToDTOs(this IQueryable<<[CurrentEntityName]>Entity> queryableEntities)
        {
            return queryableEntities.ToList().ConvertAll<<[CurrentEntityName]>DTO>(e => new <[CurrentEntityName]>DTO(e));
        }

        /// <summary>From the queryable object, get a list of <[CurrentEntityName]>DTO</summary>
        /// <returns>The DTO list created</returns>
        public static <[CurrentEntityName]>DTO FirstDTO(this IQueryable<<[CurrentEntityName]>Entity> queryableEntities)
        {
            <[CurrentEntityName]>DTO dto = null;
            <[CurrentEntityName]>Entity firstEntity = queryableEntities.First();
            if (firstEntity != null)
                dto = new <[CurrentEntityName]>DTO(firstEntity);
            return dto;
        }
<[NextForeach]><[EndIf]>
        #region Custom code
        <[ UserCodeRegion "CustomDTOCode" ]>
        // __LLBLGENPRO_USER_CODE_REGION_START CustomDTOCode
        // __LLBLGENPRO_USER_CODE_REGION_END
        <[ EndUserCodeRegion ]>
        #endregion
    }
}

FILE: DTO.tasks

<?xml version="1.0" ?>
<taskGroup xmlns="http://sd/llblgen/pro/taskGroupElementDefinitions.xsd" name="DTO Templates" isOptional="false" description="General group of tasks which are used DTO templates.">
    <supportedPlatforms>
        <platform name=".NET 3.5" />
    </supportedPlatforms>
    <supportedTemplateGroups>
    <templateGroup name="SelfServicing" />
    </supportedTemplateGroups>
    <taskGroup name="Create Directories">
        <task name="DTODirectoryCreator" assemblyFilename="SD.LLBLGen.Pro.TaskPerformers.dll" taskPerformerClass="SD.LLBLGen.Pro.TaskPerformers.DirectoryCreator">
            <parameters>
                <parameter name="folderToCreate" defaultValue="DTOClasses" isOptional="false" description="The folder to create" />
                <parameter name="failWhenExistent" defaultValue="false" isOptional="true" description="Flag to signal what to do when the folder already exists. Overrules clearWhenExistent" valueType="boolean" />
                <parameter name="clearWhenExistent" defaultValue="false" isOptional="true" description="Flag to signal if an existing folder has to be cleared first. Overruled by failWhenExistent" valueType="boolean" />
            </parameters>
        </task>
    </taskGroup>
    <taskGroup name="Create DTO Classes" description="Create DTO Classes">
        <task name="DTOInterfaceCreator" assemblyFilename="SD.LLBLGen.Pro.TaskPerformers.dll" taskPerformerClass="SD.LLBLGen.Pro.TaskPerformers.CodeEmitter">
            <parameters>
                <parameter isOptional="false" name="destinationFolder" defaultValue="DTOClasses" />
                <parameter isOptional="false" name="failWhenExistent" defaultValue="false" />
                <parameter isOptional="false" name="filenameFormat" defaultValue="IDTO.cs" />
                <parameter isOptional="false" name="templateID" defaultValue="SD_DTOInterfaceTemplate" />
                <parameter isOptional="false" name="emitType" defaultValue="generic" />
            </parameters>
        </task>
        <task name="DTOClassCreator" assemblyFilename="SD.LLBLGen.Pro.TaskPerformers.dll" taskPerformerClass="SD.LLBLGen.Pro.TaskPerformers.CodeEmitter">
            <parameters>
                <parameter isOptional="false" name="destinationFolder" defaultValue="DTOClasses" />
                <parameter isOptional="false" name="failWhenExistent" defaultValue="false" />
                <parameter isOptional="false" name="filenameFormat" defaultValue="[elementName]DTO.[extension]" />
                <parameter isOptional="false" name="templateID" defaultValue="SD_DTOTemplate" />
                <parameter isOptional="false" name="emitType" defaultValue="allEntities" />
            </parameters>
        </task>
        <task name="DTOExtentionsCreator" assemblyFilename="SD.LLBLGen.Pro.TaskPerformers.dll" taskPerformerClass="SD.LLBLGen.Pro.TaskPerformers.CodeEmitter">
            <parameters>
                <parameter isOptional="false" name="destinationFolder" defaultValue="DTOClasses" />
                <parameter isOptional="false" name="failWhenExistent" defaultValue="false" />
                <parameter isOptional="false" name="filenameFormat" defaultValue="DTOExtensions.cs" />
                <parameter isOptional="false" name="templateID" defaultValue="SD_DTOExtentionsTemplate" />
                <parameter isOptional="false" name="emitType" defaultValue="generic" />
            </parameters>
        </task>
    </taskGroup>
</taskGroup>

Finally, add the following to the appropriate place in your *.preset file. This will define the code generation task above within your generation preset.

<taskGroupPreset name="DTO Templates">
  <taskGroupPreset name="Create Directories">
    <taskPreset name="DTODirectoryCreator" />
  </taskGroupPreset>
  <taskGroupPreset name="Create DTO Classes">
    <taskPreset name="DTOInterfaceCreator" />
    <taskPreset name="DTOEntityInterfaceCreator" />
    <taskPreset name="DTOBaseClassCreator" />
    <taskPreset name="DTOClassCreator" />
  <taskPreset name="DTOExtentionsCreator" />
  </taskGroupPreset>
</taskGroupPreset>