Question

我想在我的LINQ查询中动态添加where子句。我具有过滤器属性名称和过滤器属性值，因此我需要构建如下内容：

var assignmentListQuery = context.Assignments;

if (!string.IsNullOrWhiteSpace(bookingStep.FilterPropertyName) && !string.IsNullOrWhiteSpace(bookingStep.FilterPropertyValue))
{
    assignmentListQuery = assignmentListQuery.Where(item => PROPERTYNAME == PROPERTYVALUE)
}

ar assignmentList = await assignmentListQuery.ToListAsync();

我试图获取属性的propertyinfo，在这里我似乎不知道。

var item = context.Set<Assignment>().First();
object value = item.GetType().GetProperty(bookingStep.FilterPropertyName).GetValue(item, null);

有人对如何创建这种where子句有想法吗？

public class Assignment
    {
        /// <summary>
        /// 
        /// </summary>
        [Display(Name = nameof(Id))]
        public int Id { get; set; }

        /// <summary>
        /// 
        /// </summary>
        [Display(Name = nameof(OrderNumber))]
        public string OrderNumber { get; set; }

        /// <summary>
        /// 
        /// </summary>
        [Display(Name = nameof(ScheduledLoading))]
        public DateTime ScheduledLoading { get; set; }

        /// <summary>
        /// 
        /// </summary>
        [Display(Name = nameof(CustomerOrderNumber))]
        public string CustomerOrderNumber { get; set; }

        /// <summary>
        /// 
        /// </summary>
        [Display(Name = nameof(ArticleNumber))]
        public string ArticleNumber { get; set; }

        /// <summary>
        /// 
        /// </summary>
        [Display(Name = nameof(Comment))]
        public string Comment { get; set; }

        [Display(Name = nameof(CustomerId))]
        public int? CustomerId { get; set; }
        [Display(Name = nameof(Customer))]
        public virtual Customer Customer { get; set; }
}

这是Assignment实体，FilterPropertyName例如“ CustomerOrderNumber”

Answer 1

谢谢大家。我使用了它

List<Assignment> assignmentList;
                    if (!string.IsNullOrWhiteSpace(bookingStep.FilterPropertyName) &&
                        !string.IsNullOrWhiteSpace(bookingStep.FilterPropertyValue))
                    {
                        assignmentList = await
                            assignmentListQuery.Where(e =>
                                EF.Property<string>(e, bookingStep.FilterPropertyName) ==
                                bookingStep.FilterPropertyValue).ToListAsync();
                    }
                    else
                    {
                        assignmentList = await assignmentListQuery.ToListAsync();
                    }

Answer 2

以@Doppelmoep答案为基础（这使我省了下来），您还可以使用特殊的EF Core EF.Functions.Like扩展名来动态生成具有动态PROPERTYNAMEs和动态SQL Like语句的SQL Like语句（带通配符-％_ [^]是类似SQL的有效通配符）：

assignmentList = await
                        assignmentListQuery.Where(e =>
                            EF.Functions.Like(EF.Property<string>(e, bookingStep.FilterPropertyName),
                             bookingStep.FilterPropertyValue)).ToListAsync();

EF Core 2.2中的动态Where子句

2 个答案: