private Func <DbDataReader, TResult> GetMaterializer <TResult>(DbDataReader reader) where TResult : class, new()
{
var root = new RootWithBindings(Expression.New(typeof(TResult)), String.Empty);
var readerParameter = Expression.Parameter(typeof(DbDataReader), "reader");
var readerIndexer = typeof(DbDataReader).GetMethod("get_Item", new[] { typeof(Int32) });
PropertyInfo propertyInfo;
for (var column = 0; column < reader.FieldCount; column++)
{
var members = reader.GetName(column).Split('.');
var currentRoot = root;
for (var index = 0; index < members.Length - 1; index++)
{
var member = members[index];
propertyInfo = currentRoot.Root.Type.GetProperty(member);
var newRoot = currentRoot.ObjectBindings.FirstOrDefault(b => b.Value.Name == member).Value;
if (newRoot == null)
{
if (propertyInfo.PropertyType.GetConstructor(Type.EmptyTypes) == null)
{
throw new MissingMemberException("No public parameterless constructor found on '" +
propertyInfo.PropertyType.FullName + "' type.");
}
// Creating new descendent object
newRoot = new RootWithBindings(Expression.New(propertyInfo.PropertyType), member);
currentRoot.ObjectBindings.Add(propertyInfo, newRoot);
}
currentRoot = newRoot;
}
// Assigning direct property on last descendent object
propertyInfo = currentRoot.Root.Type.GetProperty(members[members.Length - 1]);
if (reader[column].GetType() != propertyInfo.PropertyType &&
reader[column].GetType() != typeof(DBNull))
{
throw new InvalidCastException("Property '" + typeof(TResult).Name + "." + reader.GetName(column) + "' is of type '" +
propertyInfo.PropertyType + "' when database returned '" + reader[column].GetType() + "' value.");
}
var valueExpression = Expression.Call(readerParameter, readerIndexer, Expression.Constant(column));
currentRoot.MemberBindings.Add(Expression.Bind(propertyInfo,
Expression.Convert(
Expression.Condition(Expression.Equal(valueExpression, Expression.Constant(DBNull.Value)),
Expression.Constant(null), valueExpression),
propertyInfo.PropertyType)
)
);
}
return(Expression.Lambda <Func <DbDataReader, TResult> >(BuildTree(root), readerParameter).Compile());
}
private Expression BuildTree(RootWithBindings root)
{
var bindings = new List <MemberBinding>(root.MemberBindings);
foreach (var binding in root.ObjectBindings)
{
bindings.Add(Expression.Bind(binding.Key, BuildTree(binding.Value)));
}
return(Expression.MemberInit(root.Root, bindings));
}
