/// <summary>
/// Returns an object reader for the given type that matches the given schema.
/// </summary>
/// <param name="reader">The reader containing the schema to analyze.</param>
/// <param name="type">The type to analyze.</param>
/// <returns>An ObjectReader for the schema and type.</returns>
public static ObjectReader GetObjectReader(IDataReader reader, Type type)
{
SchemaIdentity schemaIdentity = new SchemaIdentity(reader);
SchemaMappingIdentity mappingIdentity = new SchemaMappingIdentity(schemaIdentity, type, null, SchemaMappingType.ExistingObject);
return _readerDataCache.GetOrAdd(mappingIdentity, i => new ObjectReader(i, reader));
}
/// <summary>
/// Initializes a new instance of the ObjectListDbDataReader class.
/// </summary>
/// <param name="schemaTable">The IDbDataReader schema table to use (get it from Sql Server).</param>
/// <param name="listType">The type of the list to bind to.</param>
/// <param name="list">The list of objects.</param>
public ObjectListDbDataReader(DataTable schemaTable, Type listType, IEnumerable list)
{
_schemaTable = schemaTable;
_listType = listType;
_list = list.GetEnumerator();
_isValueType = _listType.IsValueType || listType == typeof(string);
// SQL Server tells us the precision of the columns
// but the TDS parser doesn't like the ones set on money, smallmoney and date
// so we have to override them
_schemaTable.Columns["NumericScale"].ReadOnly = false;
foreach (DataRow row in _schemaTable.Rows)
{
string dataType = row["DataTypeName"].ToString();
if (String.Equals(dataType, "money", StringComparison.OrdinalIgnoreCase))
row["NumericScale"] = 4;
else if (String.Equals(dataType, "smallmoney", StringComparison.OrdinalIgnoreCase))
row["NumericScale"] = 4;
else if (String.Equals(dataType, "date", StringComparison.OrdinalIgnoreCase))
row["NumericScale"] = 0;
}
// if this is not a value type, then we need to have methods to pull values out of the object
if (!_isValueType)
{
// generate an identity for the schema and a key for our accessors
SchemaIdentity identity = new SchemaIdentity(schemaTable);
Tuple<Type, SchemaIdentity> key = new Tuple<Type, SchemaIdentity>(listType, identity);
_readerData = _readerDataCache.GetOrAdd(key, k => CreateFieldReaderData(k.Item1, k.Item2));
}
}
/// <summary>
/// Returns an object reader for the given type that matches the given schema.
/// </summary>
/// <param name="command">The command associated with the reader.</param>
/// <param name="reader">The reader containing the schema to analyze.</param>
/// <param name="type">The type to analyze.</param>
/// <returns>An ObjectReader for the schema and type.</returns>
public static ObjectReader GetObjectReader(IDbCommand command, IDataReader reader, Type type)
{
SchemaIdentity schemaIdentity = new SchemaIdentity(reader);
var key = Tuple.Create(schemaIdentity, type);
return _readerDataCache.GetOrAdd(key, k => new ObjectReader(command, k.Item2, reader));
}
/// <summary>
/// Create accessors to pull data from the object of the given type for the given schema.
/// </summary>
/// <param name="type">The type to analyze.</param>
/// <param name="identity">The schema identity to analyze.</param>
/// <returns>A list of accessor functions to get values from the type.</returns>
private FieldReaderData CreateFieldReaderData(Type type, SchemaIdentity identity)
{
FieldReaderData readerData = new FieldReaderData();
readerData.Accessors = new List<Func<object, object>>();
readerData.MemberTypes = new List<Type>();
for (int i = 0; i < identity.SchemaTable.Rows.Count; i++)
{
// get the name of the column
string name = _schemaTable.Rows[i]["ColumnName"].ToString();
// create a new anonymous method that takes an object and returns the value
var dm = new DynamicMethod(string.Format(CultureInfo.InvariantCulture, "GetValue-{0}-{1}", type.FullName, Guid.NewGuid()), typeof(object), new[] { typeof(object) }, true);
var il = dm.GetILGenerator();
il.Emit(OpCodes.Ldarg_0); // push object argument
il.Emit(OpCodes.Isinst, type); // cast object -> type
// get the value from the object
ClassPropInfo propInfo = new ClassPropInfo(type, name);
propInfo.EmitGetValue(il);
propInfo.EmitBox(il);
il.Emit(OpCodes.Ret);
readerData.MemberTypes.Add(propInfo.MemberType);
readerData.Accessors.Add((Func<object, object>)dm.CreateDelegate(typeof(Func<object, object>)));
}
return readerData;
}
