You can build an expression tree which contains creating of a new object and initializes a property of the object using Expression.MemberInit method. For example, you have the following code.
Employee e = new Employee()
{
Name = "John",
BirthDate = DateTime.Now
};
Console.WriteLine("Name {0}, DOB {1}",e.Name, e.BirthDate);
Here is the code that is required to build the same functionality using expression tree.
Expression testExpr = Expression.MemberInit(
Expression.New(typeof(Employee)),
new List<MemberBinding>() {
Expression.Bind(typeof(Employee).GetMember("Name")[0], Expression.Constant("John")),
Expression.Bind(typeof(Employee).GetMember("BirthDate")[0], Expression.Constant(DateTime.Now))
}
);
var emp = Expression.Lambda<Func<Employee>>(testExpr).Compile()();
Console.WriteLine("Name {0}, DOB {1}",emp.Name, emp.BirthDate);