在linq中对字符串列求和

Question

我有这样的疑问：

var q = from i in dbconnect.tblMaterialTenderGroups
   join b in dbconnect.tblMaterials on i.materialId equals b.materialId
   join f in dbconnect.tblFactoryRequests on b.requestId equals f.requestId
   where i.MaterialGroupId == materialGroupId && f.propertyFactoryCenteralId.Contains(facName)
   select b;

我确定我的“q”有记录，但是当我执行此查询时：

int? sum = q.Sum(g => Int32.Parse(g.requestAmount));

我收到此错误：

{ System.InvalidOperationException: 无法翻译表达式 表（tblMaterialTenderGroup）.Join（表（tblMaterial），i => i.materialId，b =>
Convert(b.materialId), (i, b) => new f_AnonymousType'2(i = i, b = b)).Join(Table(tblFactoryRequest), h_TransparentIdentifier5 => h _TransparentIdentifier5.b.requestId, f => Convert(f.requestId), (h_TransparentIdentifier5, f) => new f_AnonymousType1'2(h_TransparentIdentifier5 = h_TransparentIdentifier5, f = f)).Where(h_TransparentIdentifier6 => ((h_TransparentIdentifier6.h_TransparentIdentifier5.i.MaterialGroupId == Invoke(value(System.Func1[System.Nullable1[System.Int32]]))) AndAlso h_TransparentIdentifier6.f.propertyFactoryCenteralId.Contains(Invoke(value(System.Func`1 [System.String]))))).Select(h_TransparentIdentifier6 => h_TransparentIdentifier6. h__TransparentIdentifier5.b).Sum(g => Parse(g.requestAmount)) 到 SQL 中，无法将其视为本地表达式。

Answer 1

Int32.Parse 无法转换为 SQL。请改用Convert.ToInt32：

 int? sum = q.Sum(g => Convert.ToInt32(g.requestAmount));