How to write a T4 template to create DTO's from Entityframework 6?

Question

I have a large database from which I am using a database-first model in Entityframework. This sits on an internet server and communicates through WCF. The domain model uses all lowercase letters for the names of the entities, stored procedures, and columns/properties.

In my client applications, I wish to use the standard PascalCase for the naming convention.

Could a T4 template create the data transfer objects from the Entityframework with the correct naming convention?

If so, could someone please give me a starting point on how to write it?

Just to be clear, I am not wanting to change any of the code that the Entityframework generated, but rather add simple POCO classes with the appropriate CamelCase naming using the Entityframework model as input to another file which can then be referenced by the WCF service and perhaps by Automapper (or something similar).

Thanks for any suggestions.

• Database: PostgreSQL 9.5
• Interface to database: Npgsql 3.0.5
• .NET 4.5
• Entityframework 6.0

Answer 1

In lieu of anybody answering this and to hopefully help any other newbie like myself, here is what I did to create a T4 transform, DTOclasses.tt that yields only simple class definitions.

Note: this is NOT replacing the .tt files of the .edmx, but rather is run after the .edmx templates have produced the .edmx file. (I did not want to change any of the code used to produce the domain model).

Visual Studio 2015 Entityframework 6.0 .NET Framework 4.6.1

♦ Notes on Creating DTOclassess.tt

        This T4 transform was created by first copying the working transform used to build the entity model, MedicalOfficeModel.tt.
        Then, parts of it that were not needed for creation of POCO classes to be used for DTO's (data transfer objects) were removed.

    ♦ Changes made to DTOclassses.tt

        •   Adding "DTO" to namespace.
                public void BeginNamespace(CodeGenerationTools code)
                {
                    var codeNamespace = String.Format("{0}.{1}",code.VsNamespaceSuggestion(), "DTO");
                    if (!String.IsNullOrEmpty(codeNamespace))
                    {
                #>
                namespace <#=code.EscapeNamespace(codeNamespace)#>
                {
                <#+
                        PushIndent("    ");
                    }
                }

        •  Put all POCO classes in single file DTOclasses.cs

                <#
                EndNamespace(code);
            }

            fileManager.Process(false);             <--**False stops the splitting of classes into different files. Default is true.

            #>

        •  Change the property naming code:

                    public string Property(EdmProperty edmProperty)
                    {
                        return string.Format(
                            CultureInfo.InvariantCulture,
                            "{0} {1} {2} {{ {3}get; {4}set; }}",
                            Accessibility.ForProperty(edmProperty),
                            _typeMapper.GetTypeName(edmProperty.TypeUsage),
                            GetPascalCase(_code.Escape(edmProperty)),
                            _code.SpaceAfter(Accessibility.ForGetter(edmProperty)),
                            _code.SpaceAfter(Accessibility.ForSetter(edmProperty)));
                    }

        •  Change the class naming code:

                    public string EntityClassOpening(EntityType entity)
                    {
                        return string.Format(
                            CultureInfo.InvariantCulture,
                            "{0} {1}partial class {2}{3}",
                            Accessibility.ForType(entity),
                            _code.SpaceAfter(_code.AbstractOption(entity)),
                            GetPascalCase(_code.Escape(entity)),
                            _code.StringBefore(" : ", _typeMapper.GetTypeName(entity.BaseType)));
                    }

        •  Removed all the navigational stuff. Replaced everything above the helper functions (i.e., above <#+) with:
                            <#@ template debug="false" hostspecific="true" language="C#" #>
                            <#@ assembly name="System.Core" #>
                            <#@ import namespace="System.Linq" #>
                            <#@ import namespace="System.Text" #>
                            <#@ import namespace="System.Collections.Generic" #>
                            <#@ import namespace="System.Text.RegularExpressions" #>
                            <#@ include file="EF6.Utility.CS.ttinclude" #>
                            <#@ output extension=".cs" #>
                            <#

                            const string inputFile = @"MedicalOfficeModel.edmx";
                            var textTransform = DynamicTextTransformation.Create(this);
                            var code = new CodeGenerationTools(this);
                            var ef = new MetadataTools(this);
                            var typeMapper = new TypeMapper(code, ef, textTransform.Errors);
                            var fileManager = EntityFrameworkTemplateFileManager.Create(this);
                            var itemCollection = new EdmMetadataLoader(textTransform.Host, textTransform.Errors).CreateEdmItemCollection(inputFile);
                            var codeStringGenerator = new CodeStringGenerator(code, typeMapper, ef);

                            if (!typeMapper.VerifyCaseInsensitiveTypeUniqueness(typeMapper.GetAllGlobalItems(itemCollection), inputFile))
                            {
                                return string.Empty;
                            }

                            WriteHeader(codeStringGenerator, fileManager);

                            foreach (var entity in typeMapper.GetItemsToGenerate<EntityType>(itemCollection))
                            {
                                fileManager.StartNewFile(entity.Name + ".cs");
                                BeginNamespace(code);
                            #>
                            <#=codeStringGenerator.UsingDirectives(inHeader: false)#>
                            <#=codeStringGenerator.EntityClassOpening(entity)#>
                            {
                            <#
                                var simpleProperties = typeMapper.GetSimpleProperties(entity);
                                if (simpleProperties.Any())
                                {
                                    foreach (var edmProperty in simpleProperties)
                                    {
                            #>
                                <#=codeStringGenerator.Property(edmProperty)#>
                            <#
                                    }
                                }
                            #>
                            }
                            <#
                                EndNamespace(code);
                            }
                            fileManager.Process(false);

                            #>

        ♦  Added my helper function:
                    <#+

                        public static string GetPascalCase(string name)
                        {
                            return Regex.Replace(name, @"^\w|_\w",
                                (match) => match.Value.Replace("_", "").ToUpper());
                        }
                    #>

When all is done, this runs perfectly (in VS2015) to do exactly what I needed. :)