Диаграммы Linqpad. Комбинация Column и StackedColumn

как я понял, вы хотите что-то вроде этого ?

Requests.GroupBy(x => x.Date).Chart(c => c.Key)
    .AddYSeries(c => c.Count(x => x.Name == "Api1"), LINQPad.Util.SeriesType.StackedColumn, "Api1", false)
    .AddYSeries(c => c.Count(x => x.Name == "Api2"), name: "Api2")
    .AddYSeries(c => c.Count(x => x.Name == "Api3"), name: "Api3")
    .AddYSeries(c => c.Count(x => x.Name == "Api1" && x.Cached), LINQPad.Util.SeriesType.StackedColumn, "Api1 Cached", true)
    .AddYSeries(c => c.Count(x => x.Name == "Api2" && x.Cached), LINQPad.Util.SeriesType.StackedColumn, "Api2 Cached", true)
    .AddYSeries(c => c.Count(x => x.Name == "Api3" && x.Cached), LINQPad.Util.SeriesType.StackedColumn, "Ap3 Cached", true)
    .Dump();

Мне не удалось сделать это с помощью linqpad, поэтому я использовал внешнюю библиотеку для получения желаемого вывода в формате html:

Так это выглядит так:

void Main()
{
    var startDate = new DateTime(2019, 1,1);

    var Requests = new[]
    {
        new {Date=startDate, Name = "Api1", Cached=true },  
        new {Date=startDate, Name = "Api2", Cached=true },  
        new {Date=startDate, Name = "Api3", Cached=true },  
        new {Date=startDate, Name = "Api1", Cached=true },  
        new {Date=startDate, Name = "Api1", Cached=false }, 
        new {Date=startDate, Name = "Api2", Cached=false }, 
        new {Date=startDate, Name = "Api3", Cached=false }, 
        new {Date=startDate, Name = "Api1", Cached=false }, 
        new {Date=startDate.AddDays(1), Name = "Api3", Cached=true },   
        new {Date=startDate.AddDays(1), Name = "Api1", Cached=false },  
        new {Date=startDate.AddDays(1), Name = "Api2", Cached=true },   
        new {Date=startDate.AddDays(1), Name = "Api2", Cached=false },  
        new {Date=startDate.AddDays(1), Name = "Api1", Cached=true },   
        new {Date=startDate.AddDays(1), Name = "Api1", Cached=false },  
        new {Date=startDate.AddDays(1), Name = "Api3", Cached=true },   
    };



    var data = new Dictionary<Tuple<string, bool>,List<int>>(); 

    foreach (var val in Requests.GroupBy(x=>x.Date.ToShortDateString()))
        {
            var keyCached = Tuple.Create(val.Key, true);
            var keyNotCached = Tuple.Create(val.Key, false);

            if (!data.ContainsKey(keyCached))
            {
                data.Add(keyCached, new List<int>());
            }           
            if (!data.ContainsKey(keyNotCached))
            {
                data.Add(keyNotCached, new List<int>());
            }                       

            data[keyCached].Add(val.Count(x=>x.Cached));
            data[keyNotCached].Add(val.Count(x=>!x.Cached));            
        }



    var columns = Requests.Select(c=>c.Date.ToShortDateString());       
    var rawData= data.Select(x=>new {name =x.Key.Item1 + " " + ( x.Key.Item2 ? "Cached":"Not Cached"), stack = x.Key.Item1, data = x.Value});       
    Util.RawHtml(createHtml(columns, Newtonsoft.Json.JsonConvert.SerializeObject(rawData))).Dump();         

}

private string createHtml(IEnumerable<string> columns, string serializedData)
{
var columnsString = Newtonsoft.Json.JsonConvert.SerializeObject(columns);
var s = @"<script src = ""https://code.highcharts.com/highcharts.js""></script>
<script src = ""https://code.highcharts.com/modules/exporting.js""></script>
<script src = ""https://code.highcharts.com/modules/export-data.js""></script>

<div id = ""container"" style = ""min-width: 310px; height: 400px; margin: 0 auto""></div>

<script>
Highcharts.chart('container', {

    chart: {
        type: 'column'
    },

    title: {
        text: 'Total'
    },

    xAxis: {
        categories:"+columnsString+@"
    },

    yAxis: {
        allowDecimals: false,
        min: 0,
        title: {
            text: 'Number of calls'
        }
    },

    tooltip: {
        formatter: function () {
            return '<b>' + this.x + '</b><br/>' +
                this.series.name + ': ' + this.y + '<br/>' +
                'Total: ' + this.point.stackTotal;
        }
    },

    plotOptions: {
        column: {
            stacking: 'normal'
        }
    },

    series: "+serializedData+@"
});
</script>";

return s;

}