asp.net-mvc - 小时总数 (HH :MM) in Linq

Question

我的数据库表中有“TimeClocked”，格式为 HH.mm，我想使用 LINQ 对所有“TimeClocked”求和。

我尝试过这个聚合函数。

var data = _projectDbContext
    .Tasks
    .Where(x => x.Project.CompanyId == companyId && x.Status == true)
    .Select(e => TimeSpan.Parse(e.TimeClocked))
    .Aggregate(TimeSpan.FromMinutes(0), (total, next) => total + next)
    .ToString();

我正在使用EF Core 3.0.0。它显示这样的错误。

Processing of the LINQ expression 'Aggregate<TimeSpan, TimeSpan>(
    source: Select<TaskEntity, TimeSpan>(
        source: Where<TaskEntity>(
            source: DbSet<TaskEntity>, 
            predicate: (x) => x.Project.CompanyId == (Unhandled parameter: __companyId_0) && x.Status == True), 
        selector: (e) => Parse(e.TimeClocked)), 
    seed: (Unhandled parameter: __p_1), 
    func: (total, next) => total + next)' by 'NavigationExpandingExpressionVisitor' failed. This may indicate either a bug or a limitation in EF Core. See https://go.microsoft.com/fwlink/?linkid=2101433 for more detailed information.

如有任何帮助，我们将不胜感激。

Answer 1

发生这种情况是由于 restricted client evalution在 EF Core 3 中，因此您必须在不可翻译的表达式之前调用 AsEnumerable

var data = _projectDbContext
    .Tasks
    .Where(x => x.Project.CompanyId == companyId && x.Status == true)
    .AsEnumerable() // switches to LINQ to Objects
    .Select(e => TimeSpan.Parse(e.TimeClocked))
    .Aggregate(TimeSpan.FromMinutes(0), (total, next) => total + next)
    .ToString();