How to generate class field initialization using Roslyn

Question

I know how to create a local variable inside a method, for example:

LocalDeclarationStatement(VariableDeclaration(IdentifierName("MyClass"))
            .WithVariables(SingletonSeparatedList(VariableDeclarator(Identifier("nameOfvariable"))
                .WithInitializer(
                    EqualsValueClause(
                        ObjectCreationExpression(IdentifierName("MyClass")).WithArgumentList(arguments)
                            .WithNewKeyword(Token(SyntaxKind.NewKeyword)))))));

would give me:

MyClass nameOfvariable = new MyClass();

But say that I already created the field, and now I just want to initialize it (in a method, constructor or something else):

nameOfVariable = new MyClass();

How can I do it? I assume this is due to VariableDeclerator, but I cannot find a way to get it correctly, so I can add it to the list containing StatementSyntaxes. I can change VariableDecleration to "VariableDeclaration (IdentifierName (" ")), but this gives me an ugly extra space in front of the statement.

, Roslyn, http://roslynquoter.azurewebsites.net/, (, , ).

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myField = new MyField();

Answer 1

, , . , :

const string source = @"
using System;

class MyClass
{
    void Method()
    {
        MyClass nameOfVariable;
    }
}
";
var tree = CSharpSyntaxTree.ParseText(source);
var compilation = CSharpCompilation.Create("MyCompilation", new[] { tree }, new[] { MetadataReference.CreateFromFile(typeof(object).Assembly.Location) });
var semanticModel = compilation.GetSemanticModel(tree);
var root = tree.GetRoot();

var local = root.DescendantNodes().OfType<LocalDeclarationStatementSyntax>().First();
var declaration = local.Declaration;
var declarator = declaration.Variables.First();

var identifier = SyntaxFactory.IdentifierName("MyClass");
var objectCreationExpression = SyntaxFactory.ObjectCreationExpression(identifier, SyntaxFactory.ArgumentList(), null);
var equalsValueClause = SyntaxFactory.EqualsValueClause(objectCreationExpression);
var newDeclarator = declarator.WithInitializer(equalsValueClause).WithAdditionalAnnotations(Formatter.Annotation);
var newRoot = root.ReplaceNode(declarator, newDeclarator);
var formattedRoot = Formatter.Format(newRoot, Formatter.Annotation, new AdhocWorkspace());

Console.WriteLine(formattedRoot.GetText());
Console.Read();

: MyClass, ObjectCreationExpression. EqualsValueClause, . Formatter node, .

, , node , , :

----------------------------------------------- --------------------------------

, , AssignmentExpression ExpressionStatement. , ExpressionStatement , , .

:

internal static void Execute()
{
    const string source = @"
using System;

class MyClass
{
    void Method()
    {
        MyClass nameOfVariable, another;
    }
}
";
    var tree = CSharpSyntaxTree.ParseText(source);
    var compilation = CSharpCompilation.Create("MyCompilation", new[] { tree }, new[] { MetadataReference.CreateFromFile(typeof(object).Assembly.Location) });
    var semanticModel = compilation.GetSemanticModel(tree);
    var root = tree.GetRoot();

    var local = root.DescendantNodes().OfType<LocalDeclarationStatementSyntax>().First();
    var method = local.Ancestors().OfType<MethodDeclarationSyntax>().First();

    var variableIdentifier = SyntaxFactory.IdentifierName("nameOfVariable");
    var classIdentifier = SyntaxFactory.IdentifierName("MyClass");
    var objectCreationExpression = SyntaxFactory.ObjectCreationExpression(classIdentifier, SyntaxFactory.ArgumentList(), null);
    var assignment = SyntaxFactory.AssignmentExpression(SyntaxKind.SimpleAssignmentExpression, variableIdentifier, objectCreationExpression);
    var expressionStatement = SyntaxFactory.ExpressionStatement(assignment).WithAdditionalAnnotations(Formatter.Annotation);
    var newMethod = method.AddBodyStatements(expressionStatement);

    var newRoot = root.ReplaceNode(method.Body, newMethod.Body);
    var formattedRoot = Formatter.Format(newRoot, Formatter.Annotation, new AdhocWorkspace());

    Console.WriteLine(formattedRoot.GetText());
    Console.Read();
}

:

Answer 2

. , "AssignmentExpression", .

, :

ExpressionStatement(AssignmentExpression(SyntaxKind.SimpleAssignmentExpression, IdentifierName("myField"),
            ObjectCreationExpression(IdentifierName("MyClass")).WithArgumentList(arguments)
                .WithNewKeyword(Token(SyntaxKind.NewKeyword))));

:

myField = new Myclass(); 

, / .

, " Microsoft.CodeAnalysis.CSharp.SyntaxFactory;" SyntaxFactory .