如何在动态linq查询中获取匿名字段的总和

Question

to show sum of field in footer row of gridview i want to get sum from my dynamic list, InTopSuppliersView() is in separate assembly DAL while gridview is inside presentation layer.

Code in DAL:

public static dynamic InTopSuppliersView()
{

    var _pd = from pd in InTopSuppliers()
                join pm in PdnmasterDALC.InTopSuppliers() on pd.Pdnmasterid equals pm.Pdnmasterid
                select new
                {
                    RefNo = pm.PDNRefNo,
                    Date = pm.Date
                    Quantity = pd.QuantityApprovedUOM,
                    Rate = pd.Rate,
                    Amount = pd.Amount
                };

    return _pd;
}

Code on form:

var tmp = InTopSuppliersView();
gvPDNDetail.DataSource = tmp;
gvPDNDetail.DataBind();

gvPDNDetail.FooterRow.Cells[3].Text = tmp.SUM(o => o.Quantity).ToString();

i want to get sum of fields Quantity and Amount created dynamically in query

Answer 1

Let's see if I understood you correctly:

---

You return a dynamic from InTopSuppliersView because you want to return a list with anonymous type, right? And then you want to call .Sum on that list, but it won't work with the syntax because dynamic doesn't know what a lambda expression is ( o => o.Quantity ):

Cannot use a lambda expression as an argument to a dynamically dispatched operation without first casting it to a delegate or expression tree type

So I'm guessing you want to do something like this:

gvPDNDetail.FooterRow.Cells[3].Text = ((IEnumerable<dynamic>)tmp).Sum(o => o.Quantity).ToString();

---

Or just change the return type to IEnumerable<dynamic> , like so:

public static IEnumerable<dynamic> InTopSuppliersView()
{
    return from pd in InTopSuppliers()
           join pm in PdnmasterDALC.InTopSuppliers() on pd.Pdnmasterid equals pm.Pdnmasterid
           select new
           {
               RefNo = pm.PDNRefNo,
               Date = pm.Date
               Quantity = pd.QuantityApprovedUOM,
               Rate = pd.Rate,
               Amount = pd.Amount
           };
}

Then call it like before:

// Observe the casing on Sum
gvPDNDetail.FooterRow.Cells[3].Text = tmp.Sum(o => o.Quantity).ToString();

---

EDIT:

From your comments I think I know what's happening. You have the InTopSuppliersView method in one assembly and the form where you use it in another. I believe the anonymous type created is by default internal and thus cannot be used in another assembly. I think it will work if you use ExpandoObject instead:

public static IEnumerable<dynamic> InTopSuppliersView()
{
    var _pd = from pd in InTopSuppliers()
              join pm in PdnmasterDALC.InTopSuppliers() on pd.Pdnmasterid equals pm.Pdnmasterid
              select new { pd, pm };

    return _pd.Select(o =>
    {
        dynamic obj = new ExpandoObject();

        obj.RefNo = o.pm.PDNRefNo;
        obj.Date = o.pm.Date;
        obj.Quantity = o.pd.QuantityApprovedUOM;
        obj.Rate = o.pd.Rate;
        obj.Amount = o.pd.Amount;

        return obj;
    });
}

You could also (instead of above) use [assembly: InternalsVisibleTo("YourAssemblyName")] in the project where this method is and change "YourAssemblyName" with the assembly name of the forms project.