Expression trees (and related objects) can be generated in three ways:

• Calling the factory methods at System.Linq.Expressions.Expression
• In C#, assigning a lambda expression to an Expression<T> variable, parameter or property; the C# compiler generates an expression tree corresponding to the code of the lambda expression
• The VB compiler also generates expression trees from VB lambda expressions assigned to Expression<T>.

As part of the development of ExpressionTreeToString, I needed a comprehensive set of expression trees to test the renderers against. This set of objects is available as a Nuget package.

Each expression object is a field with the TestObject attribute applied to it.

The objects are available by referencing the NuGet package, and calling the static Get method:

// using ExpressionTreeTestObjects;

(string category, string source, string name, object o)[] lst = Objects.Get();

where source is the type where the object is defined -- one of the following:

Source	Description
Factory methods	Factory methods
CSCompiler	C# compiler
VBCompiler	VB compiler

and category is one of these values:

• Binary
• Blocks
• Conditionals
• Constants
• DebugInfos
• Defaults
• Dynamics
• Gotos
• Indexer
• Invocation
• Labels
• Lambda
• Literal
• Loops
• Member access (+ closed variables)
• Member bindings
• Method call
• New array
• Object creation and initialization
• Quoted
• Runtime variables
• Switch, CatchBlock
• Try, Catch, Finally
• Type check
• Unary

The static constructor automatically loads types in assemblies that start with ExpressionTreeTestObjects -- ExpressionTreeTestObjects.CSharp.dll, and ExpressionTreeTestObjects.VB.dll.

2. Call the static LoadType method on the containing type:

    Objects.LoadType(typeof(MyCustomType));
   

   and it will add the object. The type name becomes the source, and the field name becomes the objectName.

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The C# and VB compiler test expressions were added as I was working on the corresponding renderers. For the factory methods, I used reflection to build a list of all the methods and overloads at System.Linq.Expressions.Expression and created expressions by calling each one.

The result is pretty comprehensive, with one limitation: I didn't write test expressions for overloads which take an additional MethodInfo, like this one. This is being tracked at #20.