c# - 如何在 linq to sql 中编写不等于运算符？

Question

using (RapidWorkflowDataContext context = new RapidWorkflowDataContext())
                    {
                        var query = from w in context.WorkflowInstances
                        from c in context.Workflows 
                         where EmpWorkflowIDs.Contains((int)w.ID) && w.CurrentStateID != c.LastStateID
                         select w;

                        return query.ToList();
                    }

我有 2 个表:Workflows 和 WorkflowInstances。

Workflows 存储对象，workflowInstances 存储实例。

工作流表:ID,Name,FirstStateID,LastStateID

WorkflowInstances 表:ID,Name,WorkflowID,CurrentStateID

如何在 linq to sql 中编写查询以从 WorkflowInstances 中选择 CurrentStateID 不等于 LastStateID 的实例

Answer 1

您需要将联接修改为在 2 个表之间的相关列上，然后在 where 子句中添加您的条件，如下所示:

using (RapidWorkflowDataContext context = new RapidWorkflowDataContext())
                        {
                            var query = from w in context.WorkflowInstances
                                        join c in context.Workflows on w.WorkflowID equals c.ID
                                         where EmpWorkflowIDs.Contains((int)w.ID)
                                         && w.CurrentStateID != c.LastStateID
                                         select w;

                            return query.ToList();
                        }