public static IEnumerable <T> Where <T>(
this IMyDal <T> dal,
Expression <Func <T, bool> > predicate)
{
BinaryExpression be = predicate.Body as BinaryExpression;
var me = be.Left as MemberExpression;
if (me == null)
{
throw new InvalidOperationException("don't be silly");
}
if (me.Expression != predicate.Parameters[0])
{
throw new InvalidOperationException("direct properties only, please!");
}
string member = me.Member.Name;
object value;
switch (be.Right.NodeType)
{
case ExpressionType.Constant:
value = ((ConstantExpression)be.Right).Value;
break;
case ExpressionType.MemberAccess:
var constMemberAccess = ((MemberExpression)be.Right);
var capture = ((ConstantExpression)constMemberAccess.Expression).Value;
switch (constMemberAccess.Member.MemberType)
{
case MemberTypes.Field:
value = ((FieldInfo)constMemberAccess.Member).GetValue(capture);
break;
case MemberTypes.Property:
value = ((PropertyInfo)constMemberAccess.Member).GetValue(capture, null);
break;
default:
throw new InvalidOperationException("simple captures only, please");
}
break;
default:
throw new InvalidOperationException("more complexity");
}
return(dal.Find(member, value));
}
private readonly IMyDal dal; //MyDal dal = new MyDal();
public MyBll(IMyDal dal)
{
this.dal = dal;
}
