Question

我有这个linq查询正在进行选择，然后尝试对总数进行求和，因此在每个组键下有一个总和。值是一个字符串，我不能对字符串求和。但是当我尝试转换为int时，我收到一个错误：

LINQ to Entities无法识别方法＆＃39; Int32 ToInt32（System.String）＆＃39;方法，并且此方法无法转换为商店表达式。

 var dataSet = entities.BL_MT_CATEGORY
            .Distinct()
            .Where(d => (iGeography.FirstOrDefault() == "" || iGeography.Contains(d.Geography))
            && (iRetailer.FirstOrDefault() == "" || iRetailer.Contains(d.Retailer))
            && (iCountry.FirstOrDefault() == "" || iCountry.Contains(d.Country))
            && (iAirport.FirstOrDefault() == "" || iAirport.Contains(d.Airport))
            && (iShop.FirstOrDefault() == "" || iShop.Contains(d.StoreName))
            && (iCategory.Contains(d.Category))
            && (d.Values == "Sum of EuroValue"))
            .GroupBy(x => x.Category)
            .Select(g => new {
                C201408 = g.Sum(x => Convert.ToInt32(x.C201408))
            })
            .ToList();

Answer 1

尝试将转化移到查询之外。

var dataSet = entities.BL_FERRERO_MT_CATEGORY
        .Distinct()
        .Where(d => (iGeography.FirstOrDefault() == "" || iGeography.Contains(d.Geography))
        && (iRetailer.FirstOrDefault() == "" || iRetailer.Contains(d.Retailer))
        && (iCountry.FirstOrDefault() == "" || iCountry.Contains(d.Country))
        && (iAirport.FirstOrDefault() == "" || iAirport.Contains(d.Airport))
        && (iShop.FirstOrDefault() == "" || iShop.Contains(d.StoreName))
        && (iCategory.Contains(d.Category))
        && (d.Values == "Sum of EuroValue"))
        .ToList()
        .GroupBy(x => x.Category)
        .Select(g => new {
            C201408 = g.Sum(x => Convert.ToInt32(x.C201408))});

这是使LINQ to Entities转换有效查询。之后，它将执行.Sum()的分组和选择。

Answer 2

仅获取您要求和的列，并使其成为总和。

var dataSet = entities.BL_FERRERO_MT_CATEGORY
        .Distinct()
        .Where(d => (iGeography.FirstOrDefault() == "" || iGeography.Contains(d.Geography))
        && (iRetailer.FirstOrDefault() == "" || iRetailer.Contains(d.Retailer))
        && (iCountry.FirstOrDefault() == "" || iCountry.Contains(d.Country))
        && (iAirport.FirstOrDefault() == "" || iAirport.Contains(d.Airport))
        && (iShop.FirstOrDefault() == "" || iShop.Contains(d.StoreName))
        && (iCategory.Contains(d.Category))
        && (d.Values == "Sum of EuroValue"))
        .Select(x=>x.C201408)
        .ToList()
        .Sum(x=>int.Parse(x));

LINQ将字符串转换为int

2 个答案: