代码之家 › 专栏 › 技术社区 › nuyuljana

如何在Where方法中纳入标准?

linq c#

nuyuljana · 技术社区 · 9 年前

我想询问搜索命令中的WHERE条件。我在搜索期间调用web服务(API),我想在代码中放入WHERE语句,但出现了一个错误。

    private async Task CallApi(string searchText = null)     
    {           
        long lastUpdatedTime = 0;                           
        long.TryParse(AppSettings.ComplaintLastUpdatedTick, out lastUpdatedTime);

        var currentTick = DateTime.UtcNow.Ticks;            
        var time = new TimeSpan(currentTick - lastUpdatedTime);


        if (time.TotalSeconds > 1)          {
            int staffFk = Convert.ToInt32(StaffId);
            var result = await mDataProvider.GetComplaintList(lastUpdatedTime, mCts.Token, staffFk);
            if (result.IsSuccess)
            {

                // Save last updated time
                AppSettings.ComplaintLastUpdatedTick = result.Data.Updated.ToString();

                // Store data into database
                if ((result.Data.Items != null) &&
                    (result.Data.Items.Count > 0))
                {

                    var datas = new List<Complaint>(result.Data.Items);

                    **if (!string.IsNullOrEmpty(searchText))
                        {
                            datas = datas.Where(i => i.Description.Contains(searchText)
                                                 && (i.SupervisorId.Equals(StaffId))
                                                || (i.ProblemTypeName.Contains(searchText)));
                        }
                    else
                        {
                            datas = datas.Where(i => i.SupervisorId.Equals(StaffId));
                        }**

                    Datas = new ObservableCollection<Complaint>(datas);
                }
            }
            else if (result.HasError)
            {
                await mPageDialogService.DisplayAlertAsync("Error", result.ErrInfo.Message, "OK");
            }           
     }      
}

两项任务 datas 在 if ... else System.Collections.Generic.IEnumerable<ECS.Features.Complaints.Complaint>' to 'System.Collections.Generic.List<ECS.Features.Complaints.Complaint>'. An explicit conversions exists (are you missing a cast?) 编译错误:

2 回复 | 直到 9 年前

Nkosi 9 年前

datas 是一个 List<Complaint> 但是你试着把它重新分配给 IEnumerable<Complaint> Where 陈述添加 ToList() 在Where to maintain type之后,

数据 像 IEnumerable<投诉>

IEnumerable<Complaint> datas = new List<Complaint>(result.Data.Items);

AndrewP 9 年前

问题是 datas List<Complaint> 的返回类型 datas.Where(...)

你可以做:

datas = datas.Where(i => i.SupervisorId.Equals(StaffId)).ToList();

private async Task CallApi(string searchText = null)     
    {           
        long lastUpdatedTime = 0;                           
        long.TryParse(AppSettings.ComplaintLastUpdatedTick, out lastUpdatedTime);

        var currentTick = DateTime.UtcNow.Ticks;            
        var time = new TimeSpan(currentTick - lastUpdatedTime);


        if (time.TotalSeconds > 1)          {
            int staffFk = Convert.ToInt32(StaffId);
            var result = await mDataProvider.GetComplaintList(lastUpdatedTime, mCts.Token, staffFk);
            if (result.IsSuccess)
            {

                // Save last updated time
                AppSettings.ComplaintLastUpdatedTick = result.Data.Updated.ToString();

                // Store data into database
                if ((result.Data.Items != null) &&
                    (result.Data.Items.Count > 0))
                {

                    var datas = new List<Complaint>(result.Data.Items);

                    if (!string.IsNullOrEmpty(searchText))
                        {
                            datas = datas.Where(i => i.Description.Contains(searchText)
                                                 && (i.SupervisorId.Equals(StaffId))
                                                || (i.ProblemTypeName.Contains(searchText))).ToList();
                        }
                    else
                        {
                            datas = datas.Where(i => i.SupervisorId.Equals(StaffId)).ToList();
                        }

                    Datas = new ObservableCollection<Complaint>(datas);
                }
            }
            else if (result.HasError)
            {
                await mPageDialogService.DisplayAlertAsync("Error", result.ErrInfo.Message, "OK");
            }           
     }      
}

下一行也会出现错误, Datas = new ObservableCollection 贝卡西 Datas 没有定义,如果你的意思是 数据