private static Expression CreateDataRowSelector(
Expression body,
Expression[] memberSelectors)
{
Dictionary <string, Type> members = new Dictionary <string, Type>();
int index = 0;
foreach (var selector in memberSelectors)
{
members.Add(string.Format("Item{0:D2}", index), selector.Type);
index++;
}
Type rowType = DataRowFactory.Create(members);
var helper = new DataRowKeyInfoHelper(rowType);
body = helper.CreateKeyFactoryExpression(memberSelectors);
return(body);
}
private Expression CreateSelector(Expression[] arguments, Type resultType)
{
if (resultType.IsArray)
{
Expression array =
Expression.NewArrayInit(
resultType.GetElementType(),
arguments);
Type listType = typeof(List <>).MakeGenericType(resultType.GetElementType());
var constr = listType
.GetConstructors()
.Where(c =>
c.GetParameters().Length == 1 &&
c.GetParameters()[0].ParameterType.IsGenericType &&
c.GetParameters()[0].ParameterType.GetGenericTypeDefinition() == typeof(IEnumerable <>))
.First();
Expression list = Expression.New(constr, array);
Expression queryable =
Expression.Call(
typeof(Queryable)
.GetMethods().Where(m => m.Name == "AsQueryable" && m.IsGenericMethod).Single()
.MakeGenericMethod(listType.GetGenericArguments()[0]),
list);
return(queryable);
}
else if (typeof(DataRow).IsAssignableFrom(resultType))
{
IKeyInfoHelper helper = new DataRowKeyInfoHelper(resultType);
return(helper.CreateKeyFactoryExpression(arguments));
}
throw new InvalidOperationException();
}