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?
This question is related to
c#
visual-studio
visual-studio-2010
resharper
code-generation
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) > 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
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 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.
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 < 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
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 <> 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 <> 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
As of Visual Studio 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.
Maybe you could try out this: http://cometaddin.codeplex.com/
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;
}
}
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.
In Visual Studio click on one of the fields -> click the light bulb -> Generate Constructors -> Select the fields
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.
For Visual Studio 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.
Source: Stackoverflow.com