// Generate a function (Func) that converts a row from the SqlDataReader into an object of type T,
// using value conversion in the ValueFromDBConverter object.
private static Func <ValueFromDBConverter, SqlDataReader, T> GenReader <T>(ValueFromDBConverter converter)
{
var dataReaderGetOrdinal = typeof(SqlDataReader).GetMethod(nameof(SqlDataReader.GetOrdinal), new[] { typeof(string) });
var dataReaderGetValue = typeof(SqlDataReader).GetMethod(nameof(SqlDataReader.GetValue), new[] { typeof(int) });
var ctor = typeof(T).GetConstructor(new Type[0]) ?? throw new ArgumentException("Type missing default constructor.");
var properties = typeof(T).GetProperties()
.Where(p => Attribute.IsDefined(p, typeof(Column)));
var dm = new DynamicMethod("Read" + typeof(T).Name, typeof(T),
new[] { typeof(ValueFromDBConverter), typeof(SqlDataReader) });
var gen = dm.GetILGenerator();
gen.DeclareLocal(typeof(T));
gen.DeclareLocal(typeof(int));
gen.DeclareLocal(typeof(object));
gen.Emit(OpCodes.Newobj, ctor); // push obj
gen.Emit(OpCodes.Stloc_0);
foreach (var property in properties)
{
var column = (Column)Attribute.GetCustomAttribute(property, typeof(Column));
var convMethod = converter.GetConvertMethod(property.PropertyType)
?? throw new ArgumentException("Unable to find converter for property.");
var setter = property.GetSetMethod()
?? throw new ArgumentException("Property missing setter.");
gen.Emit(OpCodes.Ldarg_1); // SqlDataReader
gen.Emit(OpCodes.Ldstr, column.Name);
gen.Emit(OpCodes.Callvirt, dataReaderGetOrdinal); // dataReader.GetOrdinal
gen.Emit(OpCodes.Stloc_1);
gen.Emit(OpCodes.Ldarg_1); // SqlDataReader
gen.Emit(OpCodes.Ldloc_1);
gen.Emit(OpCodes.Callvirt, dataReaderGetValue); // dataReader.GetValue
gen.Emit(OpCodes.Stloc_2);
gen.Emit(OpCodes.Ldloc_0); // obj
gen.Emit(OpCodes.Ldarg_0); // ValueFromDBConverter
gen.Emit(OpCodes.Ldloc_2);
//gen.Emit(OpCodes.Ldc_I4, (int)column.DbType);
gen.Emit(OpCodes.Callvirt, convMethod); // converter.GetXxx(object value, int type)
gen.Emit(OpCodes.Call, setter); // obj.Property =
// todo: cache ordinals for optimization
// todo: gracefully handle missing properties
}
gen.Emit(OpCodes.Ldloc_0);
gen.Emit(OpCodes.Ret);
return((Func <ValueFromDBConverter, SqlDataReader, T>)dm.CreateDelegate(typeof(Func <ValueFromDBConverter, SqlDataReader, T>)));
}
public SnappyEngine(string connectionString, ValueFromDBConverter valueFromDBConverter = null, ValueToDBConverter valueToDBConverter = null)
{
this.valueFromDBConverter = valueFromDBConverter ?? new ValueFromDBConverter();
this.valueToDBConverter = valueToDBConverter ?? new ValueToDBConverter();
ConnectionFactory = new SqlConnectionFactory(connectionString);
}
public SnappyEngine(ISqlConnectionFactory connectionFactory, ValueFromDBConverter valueFromDBConverter = null, ValueToDBConverter valueToDBConverter = null)
{
this.valueFromDBConverter = valueFromDBConverter ?? new ValueFromDBConverter();
this.valueToDBConverter = valueToDBConverter ?? new ValueToDBConverter();
ConnectionFactory = connectionFactory;
}
internal ObjectReader(Func <ValueFromDBConverter, SqlDataReader, T> reader,
ValueFromDBConverter valueFromDBConverter)
{
this.reader = reader;
this.valueFromDBConverter = valueFromDBConverter;
}
internal static ObjectReader <T> CreateObjectReader <T>(ValueFromDBConverter valueFromDBConverter) where T : class
{
var reader = GenReader <T>(valueFromDBConverter);
return(new ObjectReader <T>(reader, valueFromDBConverter));
}
