You can build an expression tree which contains accessing a given property or field by its name using Expression.PropertyOrField method. For example, you have the following code.
TestClass obj = new TestClass();
obj.myProperty = 60;
Console.WriteLine("Property: {0}",obj.myProperty);
Console.WriteLine("Field: {0}",obj.myField);
Here is the code that is required to build the same functionality using expression tree.
Expression propertyExpr = Expression.PropertyOrField(
Expression.Constant(obj),
"myProperty"
);
Expression fieldExpr = Expression.PropertyOrField(
Expression.Constant(obj),
"myField"
);
Console.WriteLine("Property: {0}",Expression.Lambda<Func<int>>(propertyExpr).Compile()());
Console.WriteLine("Field: {0}",Expression.Lambda<Func<int>>(fieldExpr).Compile()());