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Useful LINQ Method- GetMemberTypeChain

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Recently, I have been working on a custom LINQ provider in C#.  In a later post (when I have more time to write) I will go in depth into what I am worked on and what have I learned about writing a LINQ provider.  But for now I will present a simple function that simplified part of my work.  It is called GetMemberTypeChain (not as bad as it sounds).  Given a member access expression it will return the types of all parts of the member access chain.  What this means is that given some expression like "myObject.FieldA.FiledB" it will return a list containing the type of each field/property.

 

In addition to this the method also allows you to filter out compiler created types.  When you have a member access which is using a parameter from a FROM clause in a LINQ query the compiler will often createone or more anonymous type.  Then unknowlingly the object you are trying to access now has a few anonymous field accesses in front of it.  For my purposes I wanted to be able to easily just analyze the types of the relevant parts of the expression. 

 

So without further adieu ... GetMemberTypeChain:

 

    1: private List<Type> GetMemberTypeChain(Expression expression, bool ignoreCompilerGeneratedTypes)

    2: {

    3:     if (expression == null) return null;

    4:     if (expression.NodeType == ExpressionType.MemberAccess)

    5:     {

    6:         MemberExpression memberExpression = (MemberExpression)expression;

    7:         var result = GetMemberTypeChain(memberExpression.Expression, ignoreCompilerGeneratedTypes);

    8:         Type type = memberExpression.Type;

    9:         if (!(ignoreCompilerGeneratedTypes && IsCompilerGeneratedType(type)))

   10:             result.Add(type);

   11:         return result;

   12:     }

   13:     else if (expression.NodeType == ExpressionType.Constant || expression.NodeType == ExpressionType.Parameter)

   14:     {

   15:         var typeList = new List<CustomTypeInfo>();

   16:         Type type = expression.Type;

   17:         if (!(ignoreCompilerGeneratedTypes && IsCompilerGeneratedType(type)))

   18:             typeList.Add(type);

   19:         return typeList;

   20:     }

   21:     else

   22:     {

   23:         throw new NotSupportedException("Expression type not supported: " + expression.GetType().FullName);

   24:     }

   25: }

   26:  

   27: private bool IsCompilerGeneratedType(Type type)

   28: {

   29:     var compilerGenerateds = type.GetCustomAttributes(typeof(CompilerGeneratedAttribute), true);

   30:     return (compilerGenerateds != null && compilerGenerateds.Length > 0);

   31: }

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