/// <summary>
/// 获取是否支持数据类型。
/// </summary>
/// <param name="type"></param>
/// <returns></returns>
public static bool IsDbTypeSupported(this Type type)
{
Guard.ArgumentNull(type, "type");
type = type.GetNonNullableType();
var typeCode = Type.GetTypeCode(type);
if (ConvertManager.CanConvert(type))
{
return(true);
}
return(typeCode != TypeCode.Object &&
typeCode != TypeCode.Empty &&
typeCode != TypeCode.DBNull);
}
protected override Expression VisitColumn(ColumnExpression column)
{
if (_scope != null && _scope.TryGetValue(column, out ParameterExpression recordWrapper, out ParameterExpression dataReader, out int ordinal))
{
if (!column.Type.IsDbTypeSupported())
{
throw new InvalidCastException(SR.GetString(SRKind.InvalidCastPropertyValue, column.Type.FullName));
}
//把 ColumnExpression 换成 RecordWrapper.GetInt32(IDataReader, int) 这样的表达式
var dbType = column.MapInfo != null && column.MapInfo.DataType != null ?
(DbType)column.MapInfo.DataType : column.Type.GetDbType();
var method = RecordWrapHelper.GetMethodByOrdinal(dbType);
Expression expression = Expression.Call(recordWrapper, method, dataReader, Expression.Constant(ordinal));
//先找转换器
if (ConvertManager.CanConvert(column.Type))
{
//调用ConvertManager.GetConverter
var converter = Expression.Call(null, MethodCache.GetConverter, Expression.Constant(column.Type));
//调用 IValueConverter.ConvertFrom
expression = Expression.Convert(
Expression.Call(converter, MethodCache.ConvertFrom, expression, Expression.Constant(dbType)),
column.Type);
}
else
{
if (column.Type.IsNullableType())
{
//调用 RecordWrapper.IsDbNull 判断值是否为空
expression = Expression.Condition(
Expression.Call(recordWrapper, MethodCache.IsDbNull, dataReader, Expression.Constant(ordinal)),
Expression.Convert(Expression.Constant(null), column.Type),
Expression.Convert(expression, column.Type));
}
else if (column.Type != method.ReturnType)
{
expression = Expression.Convert(expression, column.Type);
}
}
return(expression);
}
return(column);
}
private void CompileFunction(IDataReader reader)
{
var newExp = Expression.New(typeof(T));
var mapping = GetMapping(GetDataReaderFields(reader));
var rowMapExp = Expression.Constant(RecordWrapper);
var parExp = Expression.Parameter(typeof(IDataRecord), "s");
var bindings =
mapping.Select(s =>
{
var dbType = reader.GetFieldType(s.Index);
var getValueMethod = Data.RecordWrapper.RecordWrapHelper.GetMethodByOrdinal(dbType.GetDbType());
var expression = (Expression)Expression.Call(rowMapExp, getValueMethod, new Expression[] { parExp, Expression.Constant(s.Index) });
if (ConvertManager.CanConvert(s.Info.PropertyType))
{
var converter = Expression.Call(typeof(ConvertManager), nameof(ConvertManager.GetConverter), null, Expression.Constant(s.Info.PropertyType));
expression = Expression.Call(converter, MethodCache.ConvertFrom, Expression.Convert(expression, typeof(object)), Expression.Constant(dbType.GetDbType()));
expression = Expression.Convert(expression, s.Info.PropertyType);
}
else if (s.Info.PropertyType.IsNullableType())
{
expression = Expression.Condition(
Expression.Call(parExp, MethodCache.IsDBNull, Expression.Constant(s.Index, typeof(int))),
Expression.Convert(Expression.Constant(null), s.Info.PropertyType),
Expression.Convert(expression, s.Info.PropertyType));
}
else if (dbType != s.Info.PropertyType)
{
expression = Expression.Convert(expression, s.Info.PropertyType);
}
return(Expression.Bind(s.Info, expression));
});
var expr =
Expression.Lambda <Func <IDataReader, T> >(
Expression.MemberInit(
newExp,
bindings.ToArray()),
parExp);
_funcDataRecd = expr.Compile();
}
