c# - Iterate through the properties of a lambda expression? -

how can iterate through expression , change property names based on custom attribute decorated them with?

i use following code custom attribute of property, works simple expression 1 property:

var comparison = predicate.body binaryexpression;  var member = (comparison.left.nodetype == expressiontype.convert ?             ((unaryexpression)comparison.left).operand :             comparison.left) memberexpression;  var value = comparison.right constantexpression;  var attribute = attribute.getcustomattribute(member.member, typeof(myattribute)) myattribute; var columnname = attribute.name ?? member.member.name; var columnvalue = value.value; 

edit

deriving expressionvisitor, can change property name overriding method visitmember.

is place property name used build expression?

you can implement system.linq.expressions.expressionvisitor rewrite memberexpression new mapped property. , yes visitmember place have implement remapping, 1 of advantages expression trees , visitors. weird case have deal if property's type different type of mapped property.

void main() {     var data = new list<testclass>();     data.add(new testclass()     {         firstname = "first",         lastname = "last",     });      var q = data.asqueryable().select(x => x.firstname);     var vistor = new myrewriter();      var newexpression = vistor.visit(q.expression);     var output = newexpression.tostring();     //system.collections.generic.list`1[userquery+testclass].select(x => x.lastname) }  class testclass {     [myattribute(nameof(lastname))]     public string firstname { get; set; }     public string lastname { get; set; } }  class myattribute : attribute {     public string mapto { get; }     public myattribute(string mapto)     {         mapto = mapto;     } }   class myrewriter : expressionvisitor {     protected override expression visitmember(system.linq.expressions.memberexpression node)     {         var att = node.member.getcustomattribute<myattribute>();         if (att != null)         {             var newmember = node.expression.type.getproperty(att.mapto);             if (newmember != null)             {                 return expression.property(                     visit(node.expression), // important remember visit inner expression                     newmember);             }         }          return base.visitmember(node);     } } 

you can run in linqpad test it. code assumes mapping property.