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Walkthrough: Displaying Signature Help

Note

This article applies to Visual Studio 2015. If you're looking for the latest Visual Studio documentation, see Visual Studio documentation. We recommend upgrading to the latest version of Visual Studio. Download it here

Signature Help (also known as Parameter Info) displays the signature of a method in a tooltip when a user types the parameter list start character (typically an opening parenthesis). As a parameter and parameter separator (typically a comma) are typed, the tooltip is updated to show the next parameter in bold. You can define Signature Help in the context of a language service, or you can define your own file name extension and content type and display Signature Help for just that type, or you can display Signature Help for an existing content type (for example, "text"). This walkthrough shows how to display Signature Help for the "text" content type.

Signature Help is typically triggered by typing a specific character, for example, "(" (opening parenthesis), and dismissed by typing another character, for example, ")" (closing parenthesis). IntelliSense features that are triggered by typing a character can be implemented by using a command handler for the keystrokes (the IOleCommandTarget interface) and a handler provider that implements the IVsTextViewCreationListener interface. To create the Signature Help source, which is the list of signatures that participate in Signature Help, implement the ISignatureHelpSource interface and a source provider that implements the ISignatureHelpSourceProvider interface. The providers are Managed Extensibility Framework (MEF) component parts, and are responsible for exporting the source and controller classes and importing services and brokers, for example, the ITextStructureNavigatorSelectorService, which lets you navigate in the text buffer, and the ISignatureHelpBroker, which triggers the Signature Help session.

This walkthrough shows how to implement Signature Help for a hard-coded set of identifiers. In full implementations, the language is responsible for providing that content.

Prerequisites

Starting in Visual Studio 2015, you do not install the Visual Studio SDK from the download center. It is included as an optional feature in Visual Studio setup. You can also install the VS SDK later on. For more information, see Installing the Visual Studio SDK.

Creating a MEF Project

To create a MEF project

  1. Create a C# VSIX project. (In the New Project dialog, select Visual C# / Extensibility, then VSIX Project.) Name the solution SignatureHelpTest.

  2. Add an Editor Classifier item template to the project. For more information, see Creating an Extension with an Editor Item Template.

  3. Delete the existing class files.

  4. Add the following references to the project, and make sure CopyLocal is set to false:

    Microsoft.VisualStudio.Editor

    Microsoft.VisualStudio.Language.Intellisense

    Microsoft.VisualStudio.OLE.Interop

    Microsoft.VisualStudio.Shell.14.0

    Microsoft.VisualStudio.TextManager.Interop

Implementing Signature Help Signatures and Parameters

The Signature Help source is based on signatures that implement ISignature, each of which contains parameters that implement IParameter. In a full implementation, this information would be obtained from the language documentation, but in this example, the signatures are hard-coded.

To implement the Signature Help signatures and parameters

  1. Add a class file and name it SignatureHelpSource.

  2. Add the following imports.

    using System;
    using System.Collections.Generic;
    using System.Collections.ObjectModel;
    using System.ComponentModel.Composition;
    using System.Runtime.InteropServices;
    using Microsoft.VisualStudio.Language.Intellisense;
    using Microsoft.VisualStudio.Text;
    using Microsoft.VisualStudio.Text.Editor;
    using Microsoft.VisualStudio.Utilities;
    using Microsoft.VisualStudio.Editor;
    using Microsoft.VisualStudio.Text.Operations;
    using Microsoft.VisualStudio;
    using Microsoft.VisualStudio.TextManager.Interop;
    using Microsoft.VisualStudio.OLE.Interop;
    
    Imports System
    Imports System.Collections.Generic
    Imports System.Linq
    Imports System.Text
    Imports System.Collections.ObjectModel
    Imports System.ComponentModel.Composition
    Imports System.Runtime.InteropServices
    Imports Microsoft.VisualStudio.Language.Intellisense
    Imports Microsoft.VisualStudio.Text
    Imports Microsoft.VisualStudio.Text.Editor
    Imports Microsoft.VisualStudio.Utilities
    Imports Microsoft.VisualStudio.Editor
    Imports Microsoft.VisualStudio.Text.Operations
    Imports Microsoft.VisualStudio
    Imports Microsoft.VisualStudio.TextManager.Interop
    Imports Microsoft.VisualStudio.OLE.Interop
    
  3. Add a class named TestParameter that implements IParameter.

    internal class TestParameter : IParameter
    
    Friend Class TestParameter
        Implements IParameter
    
  4. Add a constructor that sets all the properties.

    public TestParameter(string documentation, Span locus, string name, ISignature signature)
    {
        Documentation = documentation;
        Locus = locus;
        Name = name;
        Signature = signature;
    }
    
    Public Sub New(ByVal documentation As String, ByVal locus As Span, ByVal name As String, ByVal signature As ISignature)
        Me.privateDocumentation = documentation
        Me.privateLocus = locus
        Me.privateName = name
        Me.privateSignature = signature
    End Sub
    
  5. Add the properties of IParameter.

    public string Documentation { get; private set; }
    public Span Locus { get; private set; }
    public string Name { get; private set; }
    public ISignature Signature { get; private set; }
    public Span PrettyPrintedLocus { get; private set; }
    
    Private privateDocumentation As String
    ReadOnly Property Documentation() As String Implements IParameter.Documentation
        Get
            Return privateDocumentation
        End Get
    
    End Property
    Private privateLocus As Span
    ReadOnly Property Locus() As Span Implements IParameter.Locus
        Get
            Return privateLocus
        End Get
    End Property
    Private privateName As String
    ReadOnly Property Name() As String Implements IParameter.Name
        Get
            Return privateName
        End Get
    End Property
    Private privateSignature As ISignature
    ReadOnly Property Signature() As ISignature Implements IParameter.Signature
        Get
            Return privateSignature
        End Get
    End Property
    Private privatePrettyPrintedLocus As Span
    ReadOnly Property PrettyPrintedLocus() As Span Implements IParameter.PrettyPrintedLocus
        Get
            Return privatePrettyPrintedLocus
        End Get
    End Property
    
  6. Add a class named TestSignature that implements ISignature.

    internal class TestSignature : ISignature
    
    Friend Class TestSignature
        Implements ISignature
    
  7. Add some private fields.

    private ITextBuffer m_subjectBuffer;
    private IParameter m_currentParameter;
    private string m_content;
    private string m_documentation;
    private ITrackingSpan m_applicableToSpan;
    private ReadOnlyCollection<IParameter> m_parameters;
    private string m_printContent;
    
    Private m_subjectBuffer As ITextBuffer
    Private m_currentParameter As IParameter
    Private m_content As String
    Private m_documentation As String
    Friend m_applicableToSpan As ITrackingSpan
    Friend m_parameters As ReadOnlyCollection(Of IParameter)
    Private m_printContent As String
    
  8. Add a constructor that sets the fields and subscribes to the Changed event.

    internal TestSignature(ITextBuffer subjectBuffer, string content, string doc, ReadOnlyCollection<IParameter> parameters)
    {
        m_subjectBuffer = subjectBuffer;
        m_content = content;
        m_documentation = doc;
        m_parameters = parameters;
        m_subjectBuffer.Changed += new EventHandler<TextContentChangedEventArgs>(OnSubjectBufferChanged);
    }
    
    Friend Sub New(ByVal subjectBuffer As ITextBuffer, ByVal content As String, ByVal doc As String, ByVal parameters As ReadOnlyCollection(Of IParameter))
        m_subjectBuffer = subjectBuffer
        m_content = content
        m_documentation = doc
        m_parameters = parameters
        AddHandler m_subjectBuffer.Changed, AddressOf OnSubjectBufferChanged
    End Sub
    
  9. Declare a CurrentParameterChanged event. This event is raised when the user fills in one of the parameters in the signature.

    public event EventHandler<CurrentParameterChangedEventArgs> CurrentParameterChanged;
    
    Public Event CurrentParameterChanged As EventHandler(Of CurrentParameterChangedEventArgs) Implements ISignature.CurrentParameterChanged
    
  10. Implement the CurrentParameter property so that it raises the CurrentParameterChanged event when the property value is changed.

    public IParameter CurrentParameter
    {
        get { return m_currentParameter; }
        internal set
        {
            if (m_currentParameter != value)
            {
                IParameter prevCurrentParameter = m_currentParameter;
                m_currentParameter = value;
                this.RaiseCurrentParameterChanged(prevCurrentParameter, m_currentParameter);
            }
        }
    }
    
    ReadOnly Property CurrentParameter() As IParameter Implements ISignature.CurrentParameter
        Get
            Return m_currentParameter
        End Get
    End Property
    
  11. Add a method that raises the CurrentParameterChanged event.

    private void RaiseCurrentParameterChanged(IParameter prevCurrentParameter, IParameter newCurrentParameter)
    {
        EventHandler<CurrentParameterChangedEventArgs> tempHandler = this.CurrentParameterChanged;
        if (tempHandler != null)
        {
            tempHandler(this, new CurrentParameterChangedEventArgs(prevCurrentParameter, newCurrentParameter));
        }
    }
    
    Private Sub RaiseCurrentParameterChanged(ByVal prevCurrentParameter As IParameter, ByVal newCurrentParameter As IParameter)
        Dim tempHandler As EventHandler(Of CurrentParameterChangedEventArgs) = Me.CurrentParameterChangedEvent
        If tempHandler IsNot Nothing Then
            tempHandler(Me, New CurrentParameterChangedEventArgs(prevCurrentParameter, newCurrentParameter))
        End If
    End Sub
    
  12. Add a method that computes the current parameter by comparing the number of commas in the ApplicableToSpan to the number of commas in the signature.

    internal void ComputeCurrentParameter()
    {
        if (Parameters.Count == 0)
        {
            this.CurrentParameter = null;
            return;
        }
    
        //the number of commas in the string is the index of the current parameter
        string sigText = ApplicableToSpan.GetText(m_subjectBuffer.CurrentSnapshot);
    
        int currentIndex = 0;
        int commaCount = 0;
        while (currentIndex < sigText.Length)
        {
            int commaIndex = sigText.IndexOf(',', currentIndex);
            if (commaIndex == -1)
            {
                break;
            }
            commaCount++;
            currentIndex = commaIndex + 1;
        }
    
        if (commaCount < Parameters.Count)
        {
            this.CurrentParameter = Parameters[commaCount];
        }
        else
        {
            //too many commas, so use the last parameter as the current one.
            this.CurrentParameter = Parameters[Parameters.Count - 1];
        }
    }
    
    Friend Sub ComputeCurrentParameter()
        If Parameters.Count = 0 Then
            Me.m_currentParameter = Nothing
            Return
        End If
    
        'the number of commas in the string is the index of the current parameter
        Dim sigText As String = ApplicableToSpan.GetText(m_subjectBuffer.CurrentSnapshot)
    
        Dim currentIndex As Integer = 0
        Dim commaCount As Integer = 0
        Do While currentIndex < sigText.Length
            Dim commaIndex As Integer = sigText.IndexOf(","c, currentIndex)
            If commaIndex = -1 Then
                Exit Do
            End If
            commaCount += 1
            currentIndex = commaIndex + 1
        Loop
    
        If commaCount < Parameters.Count Then
            Me.m_currentParameter = Parameters(commaCount)
        Else
            'too many commas, so use the last parameter as the current one.
            Me.m_currentParameter = Parameters(Parameters.Count - 1)
        End If
    End Sub
    
  13. Add an event handler for the Changed event that calls the ComputeCurrentParameter() method.

    internal void OnSubjectBufferChanged(object sender, TextContentChangedEventArgs e)
    {
        this.ComputeCurrentParameter();
    }
    
    Friend Sub OnSubjectBufferChanged(ByVal sender As Object, ByVal e As TextContentChangedEventArgs)
        Me.ComputeCurrentParameter()
    End Sub
    
  14. Implement the ApplicableToSpan property. This property holds an ITrackingSpan that corresponds to the span of text in the buffer to which the signature applies.

    public ITrackingSpan ApplicableToSpan
    {
        get { return (m_applicableToSpan); }
        internal set { m_applicableToSpan = value; }
    }
    
    ReadOnly Property ApplicableToSpan() As ITrackingSpan Implements ISignature.ApplicableToSpan
        Get
            Return (m_applicableToSpan)
        End Get
    End Property
    
  15. Implement the other parameters.

    public string Content
    {
        get { return (m_content); }
        internal set { m_content = value; }
    }
    
    public string Documentation
    {
        get { return (m_documentation); }
        internal set { m_documentation = value; }
    }
    
    public ReadOnlyCollection<IParameter> Parameters
    {
        get { return (m_parameters); }
        internal set { m_parameters = value; }
    }
    
    public string PrettyPrintedContent
    {
        get { return (m_printContent); }
        internal set { m_printContent = value; }
    }
    
    ReadOnly Property Content() As String Implements ISignature.Content
        Get
            Return (m_content)
        End Get
    End Property
    
    ReadOnly Property Documentation() As String Implements ISignature.Documentation
        Get
            Return (m_documentation)
        End Get
    End Property
    
    ReadOnly Property Parameters() As ReadOnlyCollection(Of IParameter) Implements ISignature.Parameters
        Get
            Return (m_parameters)
        End Get
    End Property
    
    ReadOnly Property PrettyPrintedContent() As String Implements ISignature.PrettyPrintedContent
        Get
            Return (m_printContent)
        End Get
    End Property
    

Implementing the Signature Help Source

The Signature Help source is the set of signatures for which you provide information.

To implement the Signature Help source

  1. Add a class named TestSignatureHelpSource that implements ISignatureHelpSource.

    internal class TestSignatureHelpSource : ISignatureHelpSource
    
    Friend Class TestSignatureHelpSource
        Implements ISignatureHelpSource
    
  2. Add a reference to the text buffer.

    private ITextBuffer m_textBuffer;
    
    Private m_textBuffer As ITextBuffer
    
  3. Add a constructor that sets the text buffer and the Signature Help source provider.

    public TestSignatureHelpSource(ITextBuffer textBuffer)
    {
        m_textBuffer = textBuffer;
    }
    
    Public Sub New(ByVal textBuffer As ITextBuffer)
        m_textBuffer = textBuffer
    End Sub
    
  4. Implement the AugmentSignatureHelpSession method. In this example, the signatures are hard-coded, but in a full implementation you would get this information from the language documentation.

    public void AugmentSignatureHelpSession(ISignatureHelpSession session, IList<ISignature> signatures)
    {
        ITextSnapshot snapshot = m_textBuffer.CurrentSnapshot;
        int position = session.GetTriggerPoint(m_textBuffer).GetPosition(snapshot);
    
        ITrackingSpan applicableToSpan = m_textBuffer.CurrentSnapshot.CreateTrackingSpan(
         new Span(position, 0), SpanTrackingMode.EdgeInclusive, 0);
    
        signatures.Add(CreateSignature(m_textBuffer, "add(int firstInt, int secondInt)", "Documentation for adding integers.", applicableToSpan));
        signatures.Add(CreateSignature(m_textBuffer, "add(double firstDouble, double secondDouble)", "Documentation for adding doubles.", applicableToSpan));
    
    }
    
    Public Sub AugmentSignatureHelpSession(ByVal session As ISignatureHelpSession, ByVal signatures As IList(Of ISignature)) Implements ISignatureHelpSource.AugmentSignatureHelpSession
        Dim snapshot As ITextSnapshot = m_textBuffer.CurrentSnapshot
        Dim position As Integer = session.GetTriggerPoint(m_textBuffer).GetPosition(snapshot)
    
        Dim applicableToSpan As ITrackingSpan = m_textBuffer.CurrentSnapshot.CreateTrackingSpan(New Span(position, 0), SpanTrackingMode.EdgeInclusive, 0)
    
        signatures.Add(CreateSignature(m_textBuffer, "add(int firstInt, int secondInt)", "Documentation for adding integers.", applicableToSpan))
        signatures.Add(CreateSignature(m_textBuffer, "add(double firstDouble, double secondDouble)", "Documentation for adding doubles.", applicableToSpan))
    End Sub
    
  5. The helper method CreateSignature() is provided just for illustration.

    private TestSignature CreateSignature(ITextBuffer textBuffer, string methodSig, string methodDoc, ITrackingSpan span)
    {
        TestSignature sig = new TestSignature(textBuffer, methodSig, methodDoc, null);
        textBuffer.Changed += new EventHandler<TextContentChangedEventArgs>(sig.OnSubjectBufferChanged);
    
        //find the parameters in the method signature (expect methodname(one, two)
        string[] pars = methodSig.Split(new char[] { '(', ',', ')' });
        List<IParameter> paramList = new List<IParameter>();
    
        int locusSearchStart = 0;
        for (int i = 1; i < pars.Length; i++)
        {
            string param = pars[i].Trim();
    
            if (string.IsNullOrEmpty(param))
                continue;
    
            //find where this parameter is located in the method signature
            int locusStart = methodSig.IndexOf(param, locusSearchStart);
            if (locusStart >= 0)
            {
                Span locus = new Span(locusStart, param.Length);
                locusSearchStart = locusStart + param.Length;
                paramList.Add(new TestParameter("Documentation for the parameter.", locus, param, sig));
            }
        }
    
        sig.Parameters = new ReadOnlyCollection<IParameter>(paramList);
        sig.ApplicableToSpan = span;
        sig.ComputeCurrentParameter();
        return sig;
    }
    
    Private Function CreateSignature(ByVal textBuffer As ITextBuffer, ByVal methodSig As String, ByVal methodDoc As String, ByVal span As ITrackingSpan) As TestSignature
        Dim sig As New TestSignature(textBuffer, methodSig, methodDoc, Nothing)
        AddHandler textBuffer.Changed, AddressOf sig.OnSubjectBufferChanged
    
        'find the parameters in the method signature (expect methodname(one, two)
        Dim pars() As String = methodSig.Split(New Char() {"("c, ","c, ")"c})
        Dim paramList As New List(Of IParameter)()
    
        Dim locusSearchStart As Integer = 0
        For i As Integer = 1 To pars.Length - 1
            Dim param As String = pars(i).Trim()
    
            If String.IsNullOrEmpty(param) Then
                Continue For
            End If
    
            'find where this parameter is located in the method signature
            Dim locusStart As Integer = methodSig.IndexOf(param, locusSearchStart)
            If locusStart >= 0 Then
                Dim locus As New Span(locusStart, param.Length)
                locusSearchStart = locusStart + param.Length
                paramList.Add(New TestParameter("Documentation for the parameter.", locus, param, sig))
            End If
        Next i
    
        sig.m_Parameters = New ReadOnlyCollection(Of IParameter)(paramList)
        sig.m_ApplicableToSpan = span
        sig.ComputeCurrentParameter()
        Return sig
    End Function
    
  6. Implement the GetBestMatch method. In this example, there are just two signatures, each of which has two parameters. Therefore, this method is not required. In a fuller implementation, in which more than one Signature Help source is available, this method is used to decide whether the highest-priority Signature Help source can supply a matching signature. If it cannot, the method returns null and the next-highest-priority source is asked to supply a match.

    public ISignature GetBestMatch(ISignatureHelpSession session)
    {
        if (session.Signatures.Count > 0)
        {
            ITrackingSpan applicableToSpan = session.Signatures[0].ApplicableToSpan;
            string text = applicableToSpan.GetText(applicableToSpan.TextBuffer.CurrentSnapshot);
    
            if (text.Trim().Equals("add"))  //get only "add" 
                return session.Signatures[0];
        }
        return null;
    }
    
    Public Function GetBestMatch(ByVal session As ISignatureHelpSession) As ISignature Implements ISignatureHelpSource.GetBestMatch
        If session.Signatures.Count > 0 Then
            Dim applicableToSpan As ITrackingSpan = session.Signatures(0).ApplicableToSpan
            Dim text As String = applicableToSpan.GetText(applicableToSpan.TextBuffer.CurrentSnapshot)
    
            If text.Trim().Equals("add") Then 'get only "add"
                Return session.Signatures(0)
            End If
        End If
        Return Nothing
    End Function
    
  7. Implement the Dispose() method:

    private bool m_isDisposed;
    public void Dispose()
    {
        if (!m_isDisposed)
        {
            GC.SuppressFinalize(this);
            m_isDisposed = true;
        }
    }
    
    Private m_isDisposed As Boolean
    
    Public Sub Dispose() Implements IDisposable.Dispose
        If Not m_isDisposed Then
            GC.SuppressFinalize(Me)
            m_isDisposed = True
        End If
    End Sub
    

Implementing the Signature Help Source Provider

The Signature Help source provider is responsible for exporting the Managed Extensibility Framework (MEF) component part and for instantiating the Signature Help source.

To implement the Signature Help source provider

  1. Add a class named TestSignatureHelpSourceProvider that implements ISignatureHelpSourceProvider, and export it with a NameAttribute, a ContentTypeAttribute of "text", and an OrderAttribute of Before="default".

    [Export(typeof(ISignatureHelpSourceProvider))]
    [Name("Signature Help source")]
    [Order(Before = "default")]
    [ContentType("text")]
    internal class TestSignatureHelpSourceProvider : ISignatureHelpSourceProvider
    
    <Export(GetType(ISignatureHelpSourceProvider)), Name("Signature Help source"), Order(Before:="default"), ContentType("text")>
    Friend Class TestSignatureHelpSourceProvider
        Implements ISignatureHelpSourceProvider
    
  2. Implement TryCreateSignatureHelpSource by instantiating the TestSignatureHelpSource.

    public ISignatureHelpSource TryCreateSignatureHelpSource(ITextBuffer textBuffer)
    {
        return new TestSignatureHelpSource(textBuffer);
    }
    
    Public Function TryCreateSignatureHelpSource(ByVal textBuffer As ITextBuffer) As ISignatureHelpSource Implements ISignatureHelpSourceProvider.TryCreateSignatureHelpSource
        Return New TestSignatureHelpSource(textBuffer)
    End Function
    

Implementing the Command Handler

Signature Help is typically triggered by a ( character and dismissed by a ) character. You can handle these keystrokes by implementing a IOleCommandTarget so that it triggers a Signature Help session when it receives a ( character preceded by a known method name, and dismisses the session when it receives a ) character.

To implement the command handler

  1. Add a class named TestSignatureHelpCommand that implements IOleCommandTarget.

    internal sealed class TestSignatureHelpCommandHandler : IOleCommandTarget
    
    Friend NotInheritable Class TestSignatureHelpCommandHandler
        Implements IOleCommandTarget
    
  2. Add private fields for the IVsTextView adapter (which lets you add the command handler to the chain of command handlers), the text view, the Signature Help broker and session, a ITextStructureNavigator, and the next IOleCommandTarget.

    IOleCommandTarget m_nextCommandHandler;
    ITextView m_textView;
    ISignatureHelpBroker m_broker;
    ISignatureHelpSession m_session;
    ITextStructureNavigator m_navigator;
    
    Private m_nextCommandHandler As IOleCommandTarget
    Private m_textView As ITextView
    Private m_broker As ISignatureHelpBroker
    Private m_session As ISignatureHelpSession
    Private m_navigator As ITextStructureNavigator
    
  3. Add a constructor to initialize these fields and to add the command filter to the chain of command filters.

    internal TestSignatureHelpCommandHandler(IVsTextView textViewAdapter, ITextView textView, ITextStructureNavigator nav, ISignatureHelpBroker broker)
    {
        this.m_textView = textView;
        this.m_broker = broker;
        this.m_navigator = nav;
    
        //add this to the filter chain
        textViewAdapter.AddCommandFilter(this, out m_nextCommandHandler);
    }
    
    Friend Sub New(ByVal textViewAdapter As IVsTextView, ByVal textView As ITextView, ByVal nav As ITextStructureNavigator, ByVal broker As ISignatureHelpBroker)
        Me.m_textView = textView
        Me.m_broker = broker
        Me.m_navigator = nav
    
        'add this to the filter chain
        textViewAdapter.AddCommandFilter(Me, m_nextCommandHandler)
    End Sub
    
  4. Implement the Exec method to trigger the Signature Help session when the command filter receives a ( character after one of the known method names, and to dismiss the session when it receives a ) character while the session is still active. In every case, the command is forwarded.

    public int Exec(ref Guid pguidCmdGroup, uint nCmdID, uint nCmdexecopt, IntPtr pvaIn, IntPtr pvaOut)
    {
        char typedChar = char.MinValue;
    
        if (pguidCmdGroup == VSConstants.VSStd2K && nCmdID == (uint)VSConstants.VSStd2KCmdID.TYPECHAR)
        {
            typedChar = (char)(ushort)Marshal.GetObjectForNativeVariant(pvaIn);
            if (typedChar.Equals('('))
            {
                //move the point back so it's in the preceding word
                SnapshotPoint point = m_textView.Caret.Position.BufferPosition - 1;
                TextExtent extent = m_navigator.GetExtentOfWord(point);
                string word = extent.Span.GetText();
                if (word.Equals("add"))
                    m_session = m_broker.TriggerSignatureHelp(m_textView);
    
            }
            else if (typedChar.Equals(')') && m_session != null)
            {
                m_session.Dismiss();
                m_session = null;
            }
        }
        return m_nextCommandHandler.Exec(ref pguidCmdGroup, nCmdID, nCmdexecopt, pvaIn, pvaOut);
    }
    
    Public Function Exec(ByRef pguidCmdGroup As Guid, ByVal nCmdID As UInteger, ByVal nCmdexecopt As UInteger, ByVal pvaIn As IntPtr, ByVal pvaOut As IntPtr) As Integer Implements IOleCommandTarget.Exec
        Dim typedChar As Char = Char.MinValue
    
        If pguidCmdGroup = VSConstants.VSStd2K AndAlso nCmdID = CUInt(VSConstants.VSStd2KCmdID.TYPECHAR) Then
            typedChar = CChar(ChrW(CUShort(Marshal.GetObjectForNativeVariant(pvaIn))))
            If typedChar.Equals("("c) Then
                'move the point back so it's in the preceding word
                Dim point As SnapshotPoint = m_textView.Caret.Position.BufferPosition - 1
                Dim extent As TextExtent = m_navigator.GetExtentOfWord(point)
                Dim word As String = extent.Span.GetText()
                If word.Equals("add") Then
                    m_session = m_broker.TriggerSignatureHelp(m_textView)
                End If
    
            ElseIf typedChar.Equals(")"c) AndAlso m_session IsNot Nothing Then
                m_session.Dismiss()
                m_session = Nothing
            End If
        End If
        Return m_nextCommandHandler.Exec(pguidCmdGroup, nCmdID, nCmdexecopt, pvaIn, pvaOut)
    End Function
    
  5. Implement the QueryStatus method so that it always forwards the command.

    public int QueryStatus(ref Guid pguidCmdGroup, uint cCmds, OLECMD[] prgCmds, IntPtr pCmdText)
    {
        return m_nextCommandHandler.QueryStatus(ref pguidCmdGroup, cCmds, prgCmds, pCmdText);
    }
    
    Public Function QueryStatus(ByRef pguidCmdGroup As Guid, ByVal cCmds As UInteger, ByVal prgCmds() As OLECMD, ByVal pCmdText As IntPtr) As Integer Implements IOleCommandTarget.QueryStatus
        Return m_nextCommandHandler.QueryStatus(pguidCmdGroup, cCmds, prgCmds, pCmdText)
    End Function
    

Implementing the Signature Help Command Provider

You can provide the Signature Help command by implementing the IVsTextViewCreationListener to instantiate the command handler when the text view is created.

To implement the Signature Help command provider

  1. Add a class named TestSignatureHelpController that implements IVsTextViewCreationListener and export it with the NameAttribute, ContentTypeAttribute, and TextViewRoleAttribute.

    [Export(typeof(IVsTextViewCreationListener))]
    [Name("Signature Help controller")]
    [TextViewRole(PredefinedTextViewRoles.Editable)]
    [ContentType("text")]
    internal class TestSignatureHelpCommandProvider : IVsTextViewCreationListener
    
    <Export(GetType(IVsTextViewCreationListener)), Name("Signature Help controller"), TextViewRole(PredefinedTextViewRoles.Editable), ContentType("text")>
    Friend Class TestSignatureHelpCommandProvider
        Implements IVsTextViewCreationListener
    
  2. Import the IVsEditorAdaptersFactoryService (used to get the ITextView, given the IVsTextView object), the ITextStructureNavigatorSelectorService (used to find the current word), and the ISignatureHelpBroker (to trigger the Signature Help session).

    [Import]
    internal IVsEditorAdaptersFactoryService AdapterService;
    
    [Import]
    internal ITextStructureNavigatorSelectorService NavigatorService { get; set; }
    
    [Import]
    internal ISignatureHelpBroker SignatureHelpBroker;
    
    <Import()>
    Friend AdapterService As IVsEditorAdaptersFactoryService
    
    <Import()>
    Friend Property NavigatorService() As ITextStructureNavigatorSelectorService
    
    <Import()>
    Friend SignatureHelpBroker As ISignatureHelpBroker
    
  3. Implement the VsTextViewCreated method by instantiating the TestSignatureCommandHandler.

    public void VsTextViewCreated(IVsTextView textViewAdapter)
    {
        ITextView textView = AdapterService.GetWpfTextView(textViewAdapter);
        if (textView == null)
            return;
    
        textView.Properties.GetOrCreateSingletonProperty(
             () => new TestSignatureHelpCommandHandler(textViewAdapter,
                textView,
                NavigatorService.GetTextStructureNavigator(textView.TextBuffer),
                SignatureHelpBroker));
    }
    
    Public Sub VsTextViewCreated(ByVal textViewAdapter As IVsTextView) Implements IVsTextViewCreationListener.VsTextViewCreated
        Dim textView As ITextView = AdapterService.GetWpfTextView(textViewAdapter)
        If textView Is Nothing Then
            Return
        End If
    
        textView.Properties.GetOrCreateSingletonProperty(Function() New TestSignatureHelpCommandHandler(textViewAdapter, textView, NavigatorService.GetTextStructureNavigator(textView.TextBuffer), SignatureHelpBroker))
    End Sub
    

Building and Testing the Code

To test this code, build the SignatureHelpTest solution and run it in the experimental instance.

To build and test the SignatureHelpTest solution

  1. Build the solution.

  2. When you run this project in the debugger, a second instance of Visual Studio is instantiated.

  3. Create a text file and type some text that includes the word "add" plus an opening parenthesis.

  4. After you type the opening parenthesis, you should see a tooltip that displays a list of the two signatures for the add() method.

See Also

Walkthrough: Linking a Content Type to a File Name Extension