Question

我希望下面的查询转换为linq，以便在MVC中进行分页。

SELECT tblInvoiceMaster.InvoiceNo,
         tblCompanyMaster.CompanyId,
         tblCompanyMaster.CompanyName,
         tblInvoiceMaster.InvoiceType,
         tblInvoiceMaster.InvoiceId,
         Sum(tblInvoiceItem.Quantity * tblProductMaster.Rate)    AS TotalPrice,
         CONVERT(VARCHAR(11), tblInvoiceMaster.InvoiceDate, 113) AS InvoiceDate
  FROM   tblCompanyMaster
         INNER JOIN tblInvoiceMaster
                 ON tblCompanyMaster.CompanyId = tblInvoiceMaster.CompanyId
         INNER JOIN tblInvoiceItem
                 ON tblInvoiceMaster.InvoiceId = tblInvoiceItem.InvoiceId
         INNER JOIN tblProductMaster
                 ON tblProductMaster.ProductId = tblInvoiceItem.ProductId
  GROUP  BY tblInvoiceMaster.InvoiceNo,
            tblCompanyMaster.CompanyId,
            tblCompanyMaster.CompanyName,
            tblInvoiceMaster.InvoiceDate,
            tblInvoiceMaster.InvoiceId,
            tblInvoiceMaster.InvoiceType

等效Linq查询：

                        (from company in DbContext.tblCompanyMasters
                        join invoice in DbContext.tblInvoiceMasters
                            on company.CompanyId equals invoice.CompanyId
                        join item in DbContext.tblInvoiceItems
                            on invoice.InvoiceId equals item.InvoiceId
                        join product in DbContext.tblProductMasters
                            on item.ProductId equals product.ProductId
                        //here I was having issue for group by columns from multiple tables
                        group new { company, invoice, item, product } by new
                        {
                            invoice.InvoiceNo,
                            invoice.InvoiceDate,
                            invoice.InvoiceId,
                            invoice.InvoiceType,
                            company.CompanyId,
                            company.CompanyName,

                        } into g
                        select new
                        {
                            g.Key.CompanyId,
                            g.Key.CompanyName,
                            g.Key.InvoiceNo,
                            g.Key.InvoiceType,
                            g.Key.InvoiceId,
                            g.Key.InvoiceDate,
                            Sum = g.Sum(o => o.item.Quantity * o.product.Rate)
                        }).ToList();

我遇到了多个列GROUP BY，这些列来自不同的表并在执行乘法时执行SUM，例如：

SUM(tblInvoiceItem.Quantity * tblProductMaster.Rate)

Answer 1

group new { company, invoice, product } by new
{
    invoice.InvoiceId,
    company.CompanyId
} into g
select new 
{
    Sum = g.Sum(o => o.invoice.Quantity * o.product.Rate)
}

等等......

Answer 2

group子句返回一系列IGrouping<TKey, TElement>个对象，这些对象包含零个或多个与该组的键值匹配的项目。每个IGrouping<TKey, TElement>对象都有一个Key属性，其中存储了键值：

//...  
group new { company, invoice } by new
{
    invoice.InvoiceNo,
    invoice.InvoiceDate,
    invoice.InvoiceId,
    invoice.InvoiceType,
    company.CompanyId,
    company.CompanyName,
} into g
select new
{
   g.Key.CompanyId,
   g.Key.CompanyName,
   g.Key.InvoiceNo,
   g.Key.InvoiceType,
   g.Key.InvoiceId,
   Sum = g.Sum(o => o.invoice.Quantity * o.company.Rate)
};

SQL到Linq，在SUM和多列列组中遇到连接问题

2 个答案: