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Walkthrough: Connecting a Host to a Generated Directive Processor

You can write your own host that processes text templates. A basic custom host is demonstrated in Walkthrough: Creating a Custom Text Template Host. You could extend that host to add funtions such as generating multiple output files.

In this walkthrough, you expand your custom host so that it supports text templates that call directive processors. When you define a domain-specific language, it generates a directive processor for the domain model. The directive processor makes it easier for users to write templates that access the model, reducing the need to write assembly and import directives in the templates.

Caution noteCaution

This walkthrough builds on Walkthrough: Creating a Custom Text Template Host. Perform that walkthrough first.

This walkthrough includes the following tasks:

  • Using Domain-Specific Language Tools to generate a directive processor that is based on a domain model.

  • Connecting a custom text template host to the generated directive processor.

  • Testing the custom host with the generated directive processor.

To define a DSL, you must have installed the following components:

In addition, you must have the custom text template transformation created in Walkthrough: Creating a Custom Text Template Host.

In this walkthrough, you use the Domain-Specific Language Designer Wizard to create a domain-specific language for the solution DSLMinimalTest.

To use Domain-Specific Language Tools to generate a directive processor that is based on a domain model

  1. Create a domain-specific language solution that has the following characteristics:

    • Name: DSLMinimalTest

    • Solution template: Minimal Language

    • File extension: min

    • Company name: Fabrikam

    For more information about creating a domain-specific language solution, see How to: Create a Domain-Specific Language Solution.

  2. On the Build menu, click Build Solution.

    Important noteImportant

    This step generates the directive processor and adds the key for it in the registry.

  3. On the Debug menu, click Start Debugging.

    A second instance of Visual Studio opens.

  4. In the experimental build, in Solution Explorer, double-click the file sample.min.

    The file opens in the designer. Notice that the model has two elements, ExampleElement1 and ExampleElement2, and a link between them.

  5. Close the second instance of Visual Studio. 

  6. Save the solution, and then close the Domain-Specific Language Designer.

After you generate the directive processor, you connect the directive processor and the custom text template host that you created in Walkthrough: Creating a Custom Text Template Host.

To connect a custom text template host to the generated directive processor

  1. Open the CustomHost solution.

  2. On the Project menu, click Add Reference.

    The Add Reference dialog box opens with the .NET tab displayed.

  3. Add the following references:

    • Microsoft.VisualStudio.Modeling.Sdk.10.0

    • Microsoft.VisualStudio.Modeling.Sdk.Diagrams.10.0

    • Microsoft.VisualStudio.TextTemplating.10.0

    • Microsoft.VisualStudio.TextTemplating.Interfaces.10.0

    • Microsoft.VisualStudio.TextTemplating.Modeling.10.0

    • Microsoft.VisualStudio.TextTemplating.VSHost.10.0

  4. At the top of Program.cs or Module1.vb, add the following line of code:

    using Microsoft.Win32;
    

    Imports Microsoft.Win32
    
  5. Locate the code for the property StandardAssemblyReferences, and replace it with the following code:

    NoteNote

    In this step, you add references to the assemblies that are required by the generated directive processor that your host will support.

    //the host can provide standard assembly references
    //the engine will use these references when compiling and
    //executing the generated transformation class
    //--------------------------------------------------------------
    public IList<string> StandardAssemblyReferences
    {
        get
        {
            return new string[]
            {
                //if this host searches standard paths and the GAC
                //we can specify the assembly name like this:
                //"System"
                //since this host only resolves assemblies from the 
                //fully qualified path and name of the assembly
                //this is a quick way to get the code to give us the
                //fully qualified path and name of the System assembly
                //---------------------------------------------------------
                typeof(System.Uri).Assembly.Location,
                            typeof(System.Uri).Assembly.Location,
                typeof(Microsoft.VisualStudio.Modeling.ModelElement).Assembly.Location,
                typeof(Microsoft.VisualStudio.Modeling.Diagrams.BinaryLinkShape).Assembly.Location,
                typeof(Microsoft.VisualStudio.TextTemplating.VSHost.ITextTemplating).Assembly.Location,
                typeof(Microsoft.VisualStudio.TextTemplating.VSHost.ModelingTextTransformation).Assembly.Location
    
            };
        }
    }
    

  6. Locate the code for the function ResolveDirectiveProcessor, and replace it with the following code:

    Important noteImportant

    This code contains hard-coded references to the name of the generated directive processor to which you want to connect. You could easily make this more general, in which case it looks for all directive processors listed in the registry and tries to find a match. In that case, the host would work with any generated directive processor.

    //the engine calls this method based on the directives the user has 
            //specified it in the text template
            //this method can be called 0, 1, or more times
            //---------------------------------------------------------------------
            public Type ResolveDirectiveProcessor(string processorName)
            {
                //check the processor name, and if it is the name of the processor the 
                //host wants to support, return the type of the processor
                //---------------------------------------------------------------------
                if (string.Compare(processorName, "DSLMinimalTestDirectiveProcessor", StringComparison.InvariantCultureIgnoreCase) == 0)
                {
                    try
                    {
                        string keyName = @"Software\Microsoft\VisualStudio\10.0Exp_Config\TextTemplating\DirectiveProcessors\DSLMinimalTestDirectiveProcessor";
                        using (RegistryKey specificKey = Registry.CurrentUser.OpenSubKey(keyName))
                        {
                            if (specificKey != null)
                            {
                                List<string> names = new List<String>(specificKey.GetValueNames());
                                string classValue = specificKey.GetValue("Class") as string;
                                if (!string.IsNullOrEmpty(classValue))
                                {
                                    string loadValue = string.Empty;
                                    System.Reflection.Assembly processorAssembly = null;
                                    if (names.Contains("Assembly"))
                                    {
                                        loadValue = specificKey.GetValue("Assembly") as string;
                                        if (!string.IsNullOrEmpty(loadValue))
                                        {
                                            //the assembly must be installed in the GAC
                                            processorAssembly = System.Reflection.Assembly.Load(loadValue);
                                        }
                                    }
                                    else if (names.Contains("CodeBase"))
                                    {
                                        loadValue = specificKey.GetValue("CodeBase") as string;
                                        if (!string.IsNullOrEmpty(loadValue))
                                        {
                                            //loading local assembly
                                            processorAssembly = System.Reflection.Assembly.LoadFrom(loadValue);
                                        }
                                    }
                                    if (processorAssembly == null)
                                    {
                                        throw new Exception("Directive Processor not found");
                                    }
                                    Type processorType = processorAssembly.GetType(classValue);
                                    if (processorType == null)
                                    {
                                        throw new Exception("Directive Processor not found");
                                    }
                                    return processorType;
                                }
                            }
                        }
                    }
                    catch (Exception e)
                    {
                        //if the directive processor can not be found, throw an error
                        throw new Exception("Directive Processor not found");
                    }
                }
    
                //if the directive processor is not one this host wants to support
                throw new Exception("Directive Processor not supported");
            }
    

  7. On the File menu, click Save All.

  8. On the Build menu, click Build Solution.

To test the custom text template host, first you must write a text template that calls the generated directive processor. Then you run the custom host, pass to it the name of the text template, and verify that the directive is processed correctly.

To create a text template to test the custom host

  1. Create a text file, and name it TestTemplateWithDP.tt. You can use any text editor, such as Notepad, to create the file.

  2. Add the following to the text file:

    NoteNote

    The programming language of the text template does not need to match that of the custom host.

    Text Template Host Test
    
    <#@ template debug="true" inherits="Microsoft.VisualStudio.TextTemplating.VSHost.ModelingTextTransformation" #>
    <# //this is the call to the examplemodel directive in the generated directive processor #>
    <#@ DSLMinimalTest processor="DSLMinimalTestDirectiveProcessor" requires="fileName='<Your Path>\Sample.min'" provides="ExampleModel=ExampleModel" #>
    <# //uncomment this line to test that the host allows the engine to set the extension #>
    <# //@ output extension=".htm" #>
    
    <# //uncomment this line if you want to see the generated transformation class #>
    <# //System.Diagnostics.Debugger.Break(); #>
    <# //this code uses the results of the examplemodel directive #>
    <#
        foreach ( ExampleElement box in this.ExampleModel.Elements ) 
        { 
            WriteLine("Box: {0}", box.Name);
    
            foreach (ExampleElement linkedTo in box.Targets)
            {
                WriteLine("Linked to: {0}", linkedTo.Name);
            }
    
            foreach (ExampleElement linkedFrom in box.Sources)
            {
                WriteLine("Linked from: {0}", linkedFrom.Name);
            }
    
            WriteLine("");
        } 
    #>
    

    Text Template Host Test
    
    <#@ template debug="true" language="VB" inherits="Microsoft.VisualStudio.TextTemplating.VSHost.ModelingTextTransformation" #>
    
    <# 'this is the call to the examplemodel directive in the generated directive processor #>
    <#@ DSLMinimalTest processor="DSLMinimalTestDirectiveProcessor" requires="fileName='<Your Path>\Sample.min'" provides="ExampleModel=ExampleModel" #>
    
    <# 'Uncomment this line to test that the host allows the engine to set the extension. #>
    <# '@ output extension=".htm" #>
    
    <# 'Uncomment this line if you want to see the generated transformation class. #>
    <# 'System.Diagnostics.Debugger.Break() #>
    
    <# 'this code uses the results of the examplemodel directive #>
    
    <#    
       For Each box as ExampleElement In Me.ExampleModel.Elements 
    
           WriteLine("Box: {0}", box.Name)
    
            For Each LinkedTo as ExampleElement In box.Targets
                WriteLine("Linked to: {0}", LinkedTo.Name)
            Next
    
            For Each LinkedFrom as ExampleElement In box.Sources
                WriteLine("Linked from: {0}", LinkedFrom.Name)
            Next
            
            WriteLine("")
    
       Next 
    #>
    
  3. In the code, replace <YOUR PATH> with the path of the Sample.min file from the design-specific language you created in the first procedure.

  4. Save and close the file.

To test the custom host

  1. Open a Command Prompt window.

  2. Type the path of the executable file for the custom host, but do not press ENTER yet.

    For example, type:

    <YOUR PATH>CustomHost\bin\Debug\CustomHost.exe

    NoteNote

    Instead of typing the address, you can browse to the file CustomHost.exe in Windows Explorer, and then drag the file into the Command Prompt window.

  3. Type a space.

  4. Type the path of the text template file, and then press ENTER.

    For example, type:

    <YOUR PATH>TestTemplateWithDP.txt

    NoteNote

    Instead of typing the address, you can browse to the file TestTemplateWithDP.txt in Windows Explorer, and then drag the file into the Command Prompt window.

    The custom host application runs and starts the text template transformation process.

  5. In Windows Explorer, browse to the folder that contains the file TestTemplateWithDP.txt.

    The folder also contains the file TestTemplateWithDP1.txt.

  6. Open this file to see the results of the text template transformation.

    The results of the generated text output appears and should look like this:

    Text Template Host Test
    
    
    Box: ExampleElement1
    Linked to: ExampleElement2
    
    Box: ExampleElement2
    Linked from: ExampleElement1
    

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