[英]Get previous element with specific data (ASP.NET MVC)
I have db.我有数据库。
Here is screen这是屏幕
Here is model of db.这是db的模型。
public partial class Logging
{
public string Imei { get; set; }
public DateTime CurDateTime { get; set; }
public Nullable<System.DateTime> GPSDateTime2 { get; set; }
public Nullable<decimal> Latitude2 { get; set; }
public Nullable<decimal> Longitude2 { get; set; }
public int Speed { get; set; }
public Nullable<int> Datatype { get; set; }
public int Id { get; set; }
}
I need to find difference in minutes between entry where datatype == 1
and previous element where datatype == 2
我需要找到datatype == 1
条目和datatype == 2
前一个元素之间的分钟差异
on back-end I make this code to get all data from table在后端,我使用此代码从表中获取所有数据
using (var ctx = new GoogleMapTutorialEntities())
{
var allitems = ctx.Loggings.AsEnumerable().Select(
x => new Logging
{
Longitude2 = x.Longitude2,
Latitude2 = x.Latitude2,
CurDateTime = x.CurDateTime,
Datatype = x.Datatype
}).ToList();
}
How I can calculate difference?我如何计算差异?
You should use the Ticks
property of the DateTime
and pass it to a TimeSpan
in order to get the time difference in minutes ( TotalMinutes
).您应该使用DateTime
的Ticks
属性并将其传递给TimeSpan
以获得以分钟为单位的时差 ( TotalMinutes
)。 For example:例如:
for(int i = 1; i < yourQuery.Count; i++){
var differenceTicks = yourQuery[i].CurDateTime.Ticks - yourQuery[i-1].CurDateTime.Ticks;
var differenceInMinutes = new TimeSpan(differenceTicks).TotalMinutes;
// You can assign this value to any property within your list or
// to another list
}
Update:更新:
To filter the query with the DataType
property, you should call the .Where(...)
method and you can use it this way:要使用DataType
属性过滤查询,您应该调用.Where(...)
方法,您可以这样使用它:
var filteredQuery = query.Where(x=> x.DataType == 1 || x.DataType == 2);
Update 2:更新 2:
The problem you described in your comment is more complex and to solve this problem you need to take advantage of the Record Id/Row Identifier in actual table.您在评论中描述的问题更复杂,要解决此问题,您需要利用实际表中的记录 ID/行标识符。 Assuming that id is simply the id
property in your model, it can be done as follows:假设 id 只是模型中的id
属性,可以按如下方式完成:
var filteredQuery = query.Where(x=> x.DataType == 1 || x.DataType == 2).OrderByDescending(x=> x.id);
for(int i = 1; i < filteredQuery.Count; i++){
if(filteredQuery[i].DataType == 2 && filteredQuery[i-1].DataType == 1){
// Then calculate the difference as described
}
}
You may need to tune the conditions in the loop according to what exactly you need.您可能需要根据您的需要调整循环中的条件。
Keep in mind that you may get a result in which
DateType == 2
may not correspond toDataType == 1
as the data in between might have been already removed in the database.请记住,您可能会得到一个结果,其中DateType == 2
可能与DataType == 1
不对应,因为它们之间的数据可能已在数据库中删除。 To tackle this issue simply check if thecurrent id is equal to previous id + 1
.要解决这个问题,只需检查current id is equal to previous id + 1
。 This only works if the id is not a GUID type (not even a sequential GUID) and of course not in Alphabetic form or generated by random functions.这仅适用于 id 不是 GUID 类型(甚至不是顺序 GUID)并且当然不是字母形式或由随机函数生成的。
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