How do I generate a constructor from class fields using Visual Studio and or ReSharper

Question

I ve gotten accustomed to many of the Java IDEs  Eclipse  NetBeans  and IntelliJ IDEA  providing you with a command to generate a default constructor for a class based on the fields in the class   For example   public class Example       public decimal MyNumber   get  set        public string Description   get  set        public int SomeInteger   get  set                This is what I want generated         public Example decimal myNumber  string description  int someInteger                MyNumber   myNumber          Description   description          SomeInteger   someInteger            Having a constructor populate all of the fields of an object is such a common task in most OOP languages  I m assuming that there is a some way for me to save time writing this boilerplate code in C   I m new to the C  world  so I m wondering if I m missing something fundamental about the language  Is there some option in Visual Studio that is obvious

User · Answer

In Visual Studio 2015 Update3 I have this feature.

Just by highlighting properties and then press Ctrl + . and then press Generate Constructor.

For example, if you've highlighted two properties it will suggest you to create a constructor with two parameters and if you've selected three it will suggest one with three parameters and so on.

It also works with Visual Studio 2017 and 2019.

User · Answer

For Visual nbsp Studio nbsp 2015 I found an extension that does just this  It seems to work well and has a reasonably high amount of downloads  So if you can t or don t want to use ReSharper you can install this one instead   You can also acquire it via NuGet

User · Answer

As of Visual nbsp Studio nbsp 2017  this looks to be a built-in feature  Hit Ctrl     while your cursor is in the class body  and select  Generate Constructor  from the Quick Actions and Refactorings dropdown

User · Answer

You could write a macro to do this -- you would use Visual Studio s parser to retrieve information about the class s members   I wrote a similar macro    I ll share the code below    The macro I wrote is for copying forward all of the constructors in a base class when you inherit from it  useful for classes like Exception that have lots of overloads on the ctor    Here s my macro  again  it doesn t solve your problem  but you can probably modify to do what you want     Imports System Imports EnvDTE Imports EnvDTE80 Imports EnvDTE90 Imports EnvDTE100 Imports System Diagnostics  Public Module ConstructorEditor     Public Sub StubConstructors            adds stubs for all of the constructors in the current class s base class         Dim selection As TextSelection   DTE ActiveDocument Selection         Dim classInfo As CodeClass2   GetClassElement            If classInfo Is Nothing Then             System Windows Forms MessageBox Show  No class was found surrounding the cursor   Make sure that this file compiles and try again     Error               Return         End If          If classInfo Bases Count   0 Then             System Windows Forms MessageBox Show  No parent class was found for this class   Make sure that this file  and any file containing parent classes compiles and try again               Return         End If           setting up an undo context -- one ctrl z undoes everything         Dim closeUndoContext As Boolean   False         If DTE UndoContext IsOpen   False Then             closeUndoContext   True             DTE UndoContext Open  StubConstructorsContext   False          End If          Try             Dim parentInfo As CodeClass2   classInfo Bases Item 1              Dim childConstructors As System Collections Generic List Of CodeFunction2    GetConstructors classInfo              Dim parentConstructors As System Collections Generic List Of CodeFunction2    GetConstructors parentInfo              For Each constructor As CodeFunction2 In parentConstructors                 If Not MatchingSignatureExists constructor  childConstructors  Then                       we only want to create ctor stubs for ctors that are missing                       note  a dictionary could be more efficient  but I doubt most classes will have more than 4 or 5 ctors                        StubConstructor classInfo  constructor                  End If             Next         Finally             If closeUndoContext Then                 DTE UndoContext Close               End If         End Try     End Sub     Private Function GetConstructors ByVal classInfo As CodeClass2  As System Collections Generic List Of CodeFunction2            return a list of all of the constructors in the specified class         Dim result As System Collections Generic List Of CodeFunction2    New System Collections Generic List Of CodeFunction2          Dim func As CodeFunction2         For Each member As CodeElement2 In classInfo Members               members collection has all class members   filter out just the function members  and then of the functions  grab just the ctors             func   TryCast member  CodeFunction2              If func Is Nothing Then Continue For             If func FunctionKind   vsCMFunction vsCMFunctionConstructor Then                 result Add func              End If         Next         Return result     End Function     Private Function MatchingSignatureExists ByVal searchFunction As CodeFunction2  ByVal functions As System Collections Generic List Of CodeFunction2   As Boolean           given a function  searchFunction   searches a list of functions where the function signatures  not necessarily the names  match           return null if no match is found  otherwise returns first match         For Each func As CodeFunction In functions             If func Parameters Count  lt   searchFunction Parameters Count Then Continue For             Dim searchParam As CodeParameter2             Dim funcParam As CodeParameter2             Dim match As Boolean   True              For count As Integer   1 To searchFunction Parameters Count                 searchParam   searchFunction Parameters Item count                  funcParam   func Parameters Item count                  If searchParam Type AsFullName  lt  gt  funcParam Type AsFullName Then                     match   False                     Exit For                 End If             Next              If match Then                 Return True             End If         Next           no match found         Return False     End Function      Private Sub StubConstructor ByVal classInfo As CodeClass2  ByVal parentConstructor As CodeFunction2            adds a constructor to the current class  based upon the parentConstructor that is passed in            highly inefficient hack to position the ctor where I want it  after the last ctor in the class  if there is another ctor           note that passing zero as the position  put the ctor first  caused some problems when we were adding ctors to classes that already had ctors         Dim position As Object         Dim ctors As System Collections Generic List Of CodeFunction2    GetConstructors classInfo           If ctors Count   0 Then             position   0         Else             position   ctors Item ctors Count - 1          End If            if there are no other ctors  put this one at the top         Dim ctor As CodeFunction2   classInfo AddFunction classInfo Name  vsCMFunction vsCMFunctionConstructor  vsCMTypeRef vsCMTypeRefVoid  position  parentConstructor Access           Dim baseCall As String     base           Dim separator As String              For Each parameter As CodeParameter2 In parentConstructor Parameters             ctor AddParameter parameter Name  parameter Type  -1              baseCall    separator   parameter Name             separator                Next         baseCall                   and 1 sad hack -- appears to be no way to programmatically add the  base   calls without using direct string manipulation         Dim startPoint As TextPoint   ctor GetStartPoint           Dim endOfSignature As EditPoint   startPoint CreateEditPoint           endOfSignature EndOfLine           endOfSignature Insert baseCall          startPoint CreateEditPoint   SmartFormat endOfSignature      End Sub      Private Function GetClassElement   As CodeClass2          returns a CodeClass2 element representing the class that the cursor is within  or null if there is no class         Try             Dim selection As TextSelection   DTE ActiveDocument Selection             Dim fileCodeModel As FileCodeModel2   DTE ActiveDocument ProjectItem FileCodeModel             Dim element As CodeElement2   fileCodeModel CodeElementFromPoint selection TopPoint  vsCMElement vsCMElementClass              Return element         Catch             Return Nothing         End Try     End Function  End Module

User · Answer

Here is a macro that I use for that purpose  It will generate a constructor from fields and properties that have a private setter   Imports System Imports EnvDTE Imports EnvDTE80 Imports EnvDTE90 Imports EnvDTE90a Imports EnvDTE100 Imports System Diagnostics Imports System Collections Generic  Public Module Temp      Sub AddConstructorFromFields           DTE UndoContext Open  Add constructor from fields            Dim classElement As CodeClass  index As Integer         GetClassAndInsertionIndex classElement  index           Dim constructor As CodeFunction         constructor   classElement AddFunction classElement Name  vsCMFunction vsCMFunctionConstructor  vsCMTypeRef vsCMTypeRefVoid  index  vsCMAccess vsCMAccessPublic           Dim visitedNames As New Dictionary Of String  String          Dim element As CodeElement  parameterPosition As Integer  isFirst As Boolean   True         For Each element In classElement Children             Dim fieldType As String             Dim fieldName As String             Dim parameterName As String              Select Case element Kind                 Case vsCMElement vsCMElementVariable                     Dim field As CodeVariable   CType element  CodeVariable                      fieldType   field Type AsString                     fieldName   field Name                     parameterName   field Name TrimStart     ToCharArray                     Case vsCMElement vsCMElementProperty                     Dim field As CodeProperty   CType element  CodeProperty                      If field Setter Access   vsCMAccess vsCMAccessPrivate Then                         fieldType   field Type AsString                         fieldName   field Name                         parameterName   field Name Substring 0  1  ToLower     field Name Substring 1                      End If             End Select              If Not String IsNullOrEmpty parameterName  And Not visitedNames ContainsKey parameterName  Then                 visitedNames Add parameterName  parameterName                   constructor AddParameter parameterName  fieldType  parameterPosition                   Dim endPoint As EditPoint                 endPoint   constructor EndPoint CreateEditPoint                   endPoint LineUp                   endPoint EndOfLine                    If Not isFirst Then                     endPoint Insert Environment NewLine                  Else                     isFirst   False                 End If                  endPoint Insert String Format MemberAssignmentFormat constructor Language   fieldName  parameterName                    parameterPosition   parameterPosition   1             End If         Next          DTE UndoContext Close            Try               This command fails sometimes               DTE ExecuteCommand  Edit FormatDocument           Catch ex As Exception         End Try     End Sub     Private Sub GetClassAndInsertionIndex ByRef classElement As CodeClass  ByRef index As Integer  Optional ByVal useStartIndex As Boolean   False          Dim selection As TextSelection         selection   CType DTE ActiveDocument Selection  TextSelection           classElement   CType selection ActivePoint CodeElement vsCMElement vsCMElementClass   CodeClass           Dim childElement As CodeElement         index   0         For Each childElement In classElement Children             Dim childOffset As Integer             childOffset   childElement GetStartPoint vsCMPart vsCMPartWholeWithAttributes  AbsoluteCharOffset             If selection ActivePoint AbsoluteCharOffset  lt  childOffset Or useStartIndex Then                 Exit For             End If             index   index   1         Next     End Sub     Private ReadOnly Property MemberAssignmentFormat ByVal language As String  As String         Get             Select Case language                 Case CodeModelLanguageConstants vsCMLanguageCSharp                     Return  this  0     1                     Case CodeModelLanguageConstants vsCMLanguageVB                     Return  Me  0     1                    Case Else                     Return                End Select         End Get     End Property End Module

User · Answer

C  added a new feature in Visual Studio 2010 called generate from usage  The intent is to generate the standard code from a usage pattern  One of the features is generating a constructor based off an initialization pattern   The feature is accessible via the smart tag that will appear when the pattern is detected     For example  let   s say I have the following class  class MyType         And I write the following in my application  var v1   new MyType 42     A constructor taking an int does not exist so a smart tag will show up and one of the options will be  Generate constructor stub   Selecting that will modify the code for MyType to be the following   class MyType       private int p      public MyType int p               TODO  Complete member initialization         this p   p

User · Answer

Here s JMarsh s Visual Studio macro modified to generate a constructor based on the fields and properties in the class   Imports System Imports EnvDTE Imports EnvDTE80 Imports EnvDTE90 Imports EnvDTE100 Imports System Diagnostics Imports System Collections Generic  Public Module ConstructorEditor      Public Sub AddConstructorFromFields            Dim classInfo As CodeClass2   GetClassElement           If classInfo Is Nothing Then             System Windows Forms MessageBox Show  No class was found surrounding the cursor   Make sure that this file compiles and try again     Error               Return         End If            Setting up undo context  One Ctrl Z undoes everything         Dim closeUndoContext As Boolean   False         If DTE UndoContext IsOpen   False Then             closeUndoContext   True             DTE UndoContext Open  AddConstructorFromFields   False          End If          Try             Dim dataMembers As List Of DataMember    GetDataMembers classInfo              AddConstructor classInfo  dataMembers          Finally             If closeUndoContext Then                 DTE UndoContext Close               End If         End Try      End Sub      Private Function GetClassElement   As CodeClass2           Returns a CodeClass2 element representing the class that the cursor is within  or null if there is no class         Try             Dim selection As TextSelection   DTE ActiveDocument Selection             Dim fileCodeModel As FileCodeModel2   DTE ActiveDocument ProjectItem FileCodeModel             Dim element As CodeElement2   fileCodeModel CodeElementFromPoint selection TopPoint  vsCMElement vsCMElementClass              Return element         Catch             Return Nothing         End Try     End Function      Private Function GetDataMembers ByVal classInfo As CodeClass2  As System Collections Generic List Of DataMember           Dim dataMembers As List Of DataMember    New List Of DataMember          Dim prop As CodeProperty2         Dim v As CodeVariable2          For Each member As CodeElement2 In classInfo Members              prop   TryCast member  CodeProperty2              If Not prop Is Nothing Then                 dataMembers Add DataMember FromProperty prop Name  prop Type               End If              v   TryCast member  CodeVariable2              If Not v Is Nothing Then                 If v Name StartsWith      And Not v IsConstant Then                     dataMembers Add DataMember FromPrivateVariable v Name  v Type                   End If             End If          Next          Return dataMembers      End Function      Private Sub AddConstructor ByVal classInfo As CodeClass2  ByVal dataMembers As List Of DataMember              Put constructor after the data members         Dim position As Object   dataMembers Count            Add new constructor         Dim ctor As CodeFunction2   classInfo AddFunction classInfo Name  vsCMFunction vsCMFunctionConstructor  vsCMTypeRef vsCMTypeRefVoid  position  vsCMAccess vsCMAccessPublic           For Each dataMember As DataMember In dataMembers             ctor AddParameter dataMember NameLocal  dataMember Type  -1          Next            Assignments         Dim startPoint As TextPoint   ctor GetStartPoint vsCMPart vsCMPartBody          Dim point As EditPoint   startPoint CreateEditPoint           For Each dataMember As DataMember In dataMembers             point Insert                  dataMember Name           dataMember NameLocal         Environment NewLine          Next      End Sub      Class DataMember          Public Name As String         Public NameLocal As String         Public Type As Object          Private Sub New ByVal name As String  ByVal nameLocal As String  ByVal type As Object              Me Name   name             Me NameLocal   nameLocal             Me Type   type         End Sub          Shared Function FromProperty ByVal name As String  ByVal type As Object               Dim nameLocal As String             If Len name   gt  1 Then                 nameLocal   name Substring 0  1  ToLower   name Substring 1              Else                 nameLocal   name ToLower               End If              Return New DataMember name  nameLocal  type           End Function          Shared Function FromPrivateVariable ByVal name As String  ByVal type As Object               If Not name StartsWith      Then                 Throw New ArgumentException  Expected private variable name to start with underscore                End If              Dim nameLocal As String   name Substring 1               Return New DataMember name  nameLocal  type           End Function      End Class  End Module

User · Answer

Maybe you could try out this  http   cometaddin codeplex com

User · Answer

I m using the following trick   I select the declaration of the class with the data-members and press   Ctrl C  Shift Ctrl C  Ctrl V    The first command copies the declaration to the clipboard  The second command is a shortcut that invokes the PROGRAM The last command overwrites the selection by text from the clipboard    The PROGRAM gets the declaration from the clipboard   finds the name of the class  finds all members and their types  generates constructor and copies it all back into the clipboard   We are doing it with freshmen on my  Programming-I  practice  Charles University  Prague  and most of students gets it done till the end of the hour   If you want to see the source code  let me know

User · Answer

In Visual Studio click on one of the fields - gt  click the light bulb - gt  Generate Constructors - gt  Select the fields

User · Answer

You can do this easily with ReSharper 8 or later  The ctorf  ctorp  and ctorfp snippets generate constructors that populate all the fields  properties  or fields and properties of a class

User · Answer

ReSharper offers a Generate Constructor tool where you can select any field properties that you want initialized  I use the Alt   Ins hot-key to access this

[c#] How do I generate a constructor from class fields using Visual Studio (and/or ReSharper)?

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