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String representation of expression trees and expression tree parts + debugging visualizer
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Expression To String and Expression Tree Visualizer

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This project provides the following:


  • Star the project
  • File an issue

String representations of expression trees

Expression<Func<bool>> expr = () => true;

// prints: () => true

Console.WriteLine(expr.ToString("Visual Basic"));
// prints: Function() True

Console.WriteLine(expr.ToString("Factory methods"));
// prints:
    // using static System.Linq.Expressions.Expression


Console.WriteLine(expr.ToString("Object notation"));
// prints:
    new Expression<Func<bool>> {
        NodeType = ExpressionType.Lambda,
        Type = typeof(Func<bool>),
        Body = new ConstantExpression {
            Type = typeof(bool),
            Value = true
        ReturnType = typeof(bool)

Console.WriteLine(expr.ToString("Textual tree"));
// prints:
    Lambda (Func<bool>)
        Body - Constant (bool) = True


  • Multiple formatters (with more planned):

    • Pseudo-code in C# or VB.NET
    • Factory method calls which generate this expression
    • Object notation, using object initializer and collection initializer syntax to describe objects
    • Textual tree, focusing on the properties related to the structure of the tree
  • Extension methods are rendered as instance methods

    Expression<Func<int, int>> expr = x => Enumerable.Range(1, x).Select(y => x * y).Count();
    // prints: (int x) => Enumerable.Range(1, x).Select((int y) => x * y).Count()
  • Closed-over variables are rendered as simple identifiers (instead of member access on the hidden compiler-generated class)

    var i = 7;
    var j = 8;
    Expression<Func<int>> expr = () => i + j;
    // prints: () => i + j
  • Type names are rendered using language keywords, instead of just the type name; e.g. List<string> or List(Of Date) instead of List`1

  • Special handling of calls to String.Concat and String.Format

    var name = "World";
    Expression<Func<string>> expr = () => string.Format("Hello, {0}!", name);
    // prints: () => $"Hello, {name}!"
  • Supports the full range of types in System.Linq.Expressions, including .NET 4 expression types, and DynamicExpression

Visual Studio debugger visualizer for expression trees

The UI consists of:

  1. a graphical treeview of the expression tree structure,
  2. source code representation of the tree, and
  3. end nodes -- nodes in the tree which are not composed of other expressions: parameters, closure variables, constants and default values


You can switch formatters without reloading the visualizer:

Language switch

Selection syncing:

  • when selecting from the tree:

    Selection sync from tree

  • from source code:

    Selection sync from source code

  • and from end nodes:

    Selection sync from end nodes


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