LINQ to Entities无法识别方法'System.TimeSpan Subtract(System.DateTime) [英] LINQ to Entities does not recognize the method 'System.TimeSpan Subtract(System.DateTime)

问题描述

以下内容引发错误:

public FieldViewer GetFieldViewByFieldIDIPAndUserByDate( int fieldID, string ip, string userID, DateTime date )
{
    return this.context.FieldViewers.Where( x =>
        x.Field.FieldID == fieldID &&
        x.Viewer.IPAddress == ip &&
        x.Viewer.User.Id == userID &&

        date.Subtract( x.Viewer.CreatedAt ).TotalMinutes >= 10 ).FirstOrDefault();
}

LINQ to Entities无法识别方法'System.TimeSpan Subtract(System.DateTime)'，并且该方法无法转换为商店表达式.

LINQ to Entities does not recognize the method 'System.TimeSpan Subtract(System.DateTime)' method, and this method cannot be translated into a store expression.

如何解决此问题，因为我需要为每个查询减去.

How do I go about solving this as I need to subtract per query instead.

推荐答案

EntityFunctions.DiffMinutes对于您的情况将无效.您应该这样做

EntityFunctions.DiffMinutes for your case will be inefficient. You should do this way

public FieldViewer GetFieldViewByFieldIDIPAndUserByDate( int fieldID, string ip, string userID, DateTime date )
{
    var tenMinThreshold = date - TimeSpan.FromMinutes(10);
    return this.context.FieldViewers.Where( x =>
        x.Field.FieldID == fieldID &&
        x.Viewer.IPAddress == ip &&
        x.Viewer.User.Id == userID &&
        x.Viewer.CreatedAt <= tenMinThreshold).FirstOrDefault();
}

这篇关于LINQ to Entities无法识别方法'System.TimeSpan Subtract(System.DateTime)的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！