在MVC中，为什么HandleError或Application_Error没有捕获SqlExceptions？

Question

在MVC中，为什么HandleError（扩展与否）或Application_Error没有捕获SqlExceptions？

    public override void OnException(ExceptionContext filterContext)
    {
        int httpcode = new HttpException(null, filterContext.Exception).GetHttpCode();

        if (filterContext.ExceptionHandled || !filterContext.HttpContext.IsCustomErrorEnabled)
            return;
        if (!ExceptionType.IsInstanceOfType(filterContext.Exception))
            return;

        var er = new OEB.DataAccess.ErrorHandlerRepository();
        er.LogException("Custom - " + filterContext.Exception.ToString());

        filterContext.ExceptionHandled = true;
        switch (httpcode)
        {
            case 404:
                filterContext.Result = new RedirectResult("~/ErrorHandler/NotFound");
                break;
            case 500:
                filterContext.Result = new RedirectResult("~/ErrorHandler/ServerError");
                break;
            default:
                filterContext.Result = new RedirectResult("~/ErrorHandler/General");
                break;
        }            
    }

我在Filter.Config中注册了这个：

public class FilterConfig
{
    public static void RegisterGlobalFilters(GlobalFilterCollection filters)
    {
        filters.Add(new CustomErrorHandlerAttribute());
    }
}

我正在使用Dapper，并尝试从无效插入中捕获SQLException（AspNetRoles2不存在），并获得正常的黄色屏幕：

    public bool CreateRole(string roleName)
    {
        int rowsAffected = Execute("INSERT into AspNetRoles2 (RoleName) VALUES (@roleName)", new { roleName = roleName });
        return rowsAffected == 1 ? true : false;
    }

    protected int Execute(string sp, object parameters = null)
    {
            using (var scope = new TransactionScope())
            {
                using (var conn = new SqlConnection(secConnStr))
                {
                    rowsAffectedCount = conn.Execute(sp, parameters);
                }
                scope.Complete();
            }
     }