Reset Count - If different value in specific column using C# lambda expression-CodePudding

Is there a way to reset count after select? Here is sample in Fiddle.

This is the result I'm getting,

{groupRowId: 1, monthYear: '2020-08', projectName: 'Project 1'}
{groupRowId: 2, monthYear: '2020-08', projectName: 'Project 2'}
{groupRowId: 3, monthYear: '2020-08', projectName: 'Project 3'}
{groupRowId: 4, monthYear: '2021-08', projectName: 'Project 4'}
{groupRowId: 5, monthYear: '2021-08', projectName: 'Project 5'}
{groupRowId: 6, monthYear: '2021-08', projectName: 'Project 6'}

This is what I've tried.

public List<object> GenerateDynamicCalendar(List<ProjectResult> result) {
            int row = 1;
     var queryAug = result.Where(c => c.LiveDate != Convert.ToDateTime("1900-01-01 00:00:00.000") && c.LiveDate.Month == 8)
              .GroupBy(c => new { c.Month, c.Name})
              .Select(g => new DynamicProjectCalendarAug
              {
                  GroupRowId = row  ,
                  MonthYear = g.Key.Month,
                  ProjectName = g.Key.Name,
                  Aug = g.Where(c => c.LiveDate != Convert.ToDateTime("1900-01-01 00:00:00.000") && c.LiveDate.Month == 8).Max(c => c.Name)
              }).ToList();
        
            List<object> query = otherMonthResult.Cast<object>()
                .Concat(queryAug)
            return query;
    }

And this is what I want to achieve. Since MonthYear value is different I want to reset count back to 1

{groupRowId: 1, monthYear: '2020-08', projectName: 'Project 1'}
{groupRowId: 2, monthYear: '2020-08', projectName: 'Project 2'}
{groupRowId: 3, monthYear: '2020-08', projectName: 'Project 3'}
{groupRowId: 1, monthYear: '2021-08', projectName: 'Project 4'}
{groupRowId: 2, monthYear: '2021-08', projectName: 'Project 5'}
{groupRowId: 3, monthYear: '2021-08', projectName: 'Project 6'}

CodePudding user response：

If you group by only month, you could use the .GroupBy()'s resultSelector to create a DynamicProjectCalendarAug object for each group item. The resultSelector takes advantage of the .Select() overload that provides the index of the source element. It would look like the following:

var queryAug = result
    //.Where( ... )
    .GroupBy(
        resultItem => resultItem.Month,
        ( _, itemsInMonth ) => itemsInMonth
             .Select(( item, i ) => new DynamicProjectCalendarAug {
                 GroupRowId = i   1,
                 MonthYear = item.Month,
                 ProjectName = item.Name,
                 //Aug = ...
             }))
    .SelectMany(_ => _)
    .ToList();

For a simplified implementation of your classes, this example input:

List<ProjectResult> result = new()
{
    new() { Month = "2020-08", Name = "Project 1"},
    new() { Month = "2020-08", Name = "Project 2"},
    new() { Month = "2020-08", Name = "Project 3"},
    new() { Month = "2021-08", Name = "Project 4"},
    new() { Month = "2021-08", Name = "Project 5"},
    new() { Month = "2021-08", Name = "Project 6"}
};

will have the following output:

1  |  2020-08  |  Project 1
2  |  2020-08  |  Project 2
3  |  2020-08  |  Project 3
1  |  2021-08  |  Project 4
2  |  2021-08  |  Project 5
3  |  2021-08  |  Project 6

Example fiddle here.

CodePudding user response：

Created an example to show how you can solve this. https://dotnetfiddle.net/b9mnau

CodePudding user response：

Having

record WithRowId(int GroupRowId, MyDto MyDto);
record MyDto(int X, string Val);

var list = new []{ 
    new MyDto(X: 1, Val: "a"),
    new MyDto(X: 1, Val: "b"),
    new MyDto(X: 2, Val: "c"),
    new MyDto(X: 2, Val: "d"),
};

you could add group row id the following ways:

var list2 = new List<WithRowId>();
foreach( var group in list.GroupBy( c => c.X ))
{
    int i = 0;
    foreach(var r in group)
    {
        list2.Add(new WithRowId(1   i  , r));
    }
}


// Method 2
var list2B = list
 .GroupBy( c => c.X)
 .SelectMany( g => g.Select((x, i) => new WithRowId(GroupRowId: i 1, MyDto: x)));

The second method uses the lesser known variant of Select which provides an index.