Blazor component flex lines go outside of the component layout

I created blazor calendar component which consists of two parts Header and weekview components. The component flex lines go beyond the component itself and I could not figure out Why? I have attached a screenshot of the issue.

Header (Calendar Component) code

<div class="maincontainer">

    <div class="viewtitle">Augest 2022</div>

    <div class="lbuttons">
        <button class="button">&#60;</button>
        <button class="button">&#62;</button>
        <button class="button">Today</button>
    </div>

    <div class="mbuttons">
        <label class="datelabel">Monady, Augest 21, 2022</label>
        <input class="dateinput" type="datetime-local" id="schedule-time"
               name="schedule-time" value="2022-06-12T19:30"
               min="2022-06-07T00:00" max="2022-06-14T00:00">
        <input class="button" type="button" id="btnsubmit" value="Submit">
    </div>

    <div class="rbuttons">
        <button class="button" @onclick="@(() => DayView_Click())" @onclick:stopPropagation="true">Day</button>
        <button class="button" @onclick="@(() => WeekView_Click())" @onclick:stopPropagation="true">Week</button>
        <button class="button" @onclick="@(() => MonthView_Click())" @onclick:stopPropagation="true">Month</button>
    </div>
</div>


@switch (CurrentView)
{
    case CalendarViewOption.MonthView:
        <MonthViewComponent></MonthViewComponent>
        break;
    case CalendarViewOption.DayView:  
        <DayViewComponent></DayViewComponent>
        break;
    
    case CalendarViewOption.WeekView:
        <WeekViewComponent></WeekViewComponent>
        break;

}

CSS

body {
    margin: 0;
    padding: 0;
}

.maincontainer {
    background: #E7EAF6;
    display: grid;
    grid-template-columns: minmax(100px, 1fr) auto minmax(100px, 1fr);
    grid-template-rows: auto
}

.viewtitle {
    grid-column: 1/4;
    grid-row: 1;
    justify-self: center;
    padding: 5px 5px 5px 5px;
    color: darkblue;
    font-weight: bold;
    font-size: 16px;
}

.lbuttons {
    grid-column: 1/2;
    grid-row: 2;
    justify-self: start;
}

.mbuttons {
    grid-column: 2/3;
    grid-row: 2;
    justify-self: center;
}

.rbuttons {
    grid-column: 3/4;
    grid-row: 2;
    justify-self: end;
}

.button {
    background-color: black;
    color: white;
    border: 2px solid #555555;
    padding: 3px;
    margin: 0;
    box-shadow: 0 8px 16px 0 rgba(0,0,0,0.2), 0 6px 20px 0 rgba(0,0,0,0.19);
    border-radius: 5px;
    cursor: pointer;
}

.button:hover {
    background-color: white;
    color: black;
}

.datelabel {
    color: black;
    font-weight: bold;
}

.dateinput {
    padding: 3px 3px;
    margin: 2px 0;
    border: 1px solid rgb(130, 128, 128);
    border-radius: 4px;
    box-sizing: border-box;
    cursor: pointer;
}

WeekView

<div class="calendar-container">

    <div class="header">
        <ul class="weekdays">
            <li>Sun</li>
            <li>Mon</li>
            <li>Tue</li>
            <li>Wed</li>
            <li>Thu</li>
            <li>Fri</li>
            <li>Sat</li>
        </ul>

        <ul class="daynumbers">
            <li>20</li>
            <li>21</li>
            <li>22</li>
            <li>23</li>
            <li>24</li>
            <li>25</li>
            <li>26</li>
        </ul>
    </div>

    <div class="timeslots-container">
        <ul class="timeslots">
            <li>8<sup>am</sup></li>
            <li>9<sup>am</sup></li>
            <li>10<sup>am</sup></li>
            <li>11<sup>am</sup></li>
            <li>12<sup>pm</sup></li>
            <li>4<sup>pm</sup></li>
            <li>5<sup>pm</sup></li>
            <li>6<sup>pm</sup></li>
            <li>7<sup>pm</sup></li>
            <li>8<sup>pm</sup></li>
            <li>9<sup>pm</sup></li>
            <li>10<sup>pm</sup></li>
        </ul>
    </div>

    <div class="event-container">
        <div class="slot slot-1">
            <div class="event-staus"></div>
            <span>Event A</span>
        </div>

        <div class="slot slot-2" style="height: 60px; grid-row: 1; grid-column: 1;">
            <div class="event-staus"></div>
            <span>Event A</span>
        </div>
    </div>

CSS

body {
    margin: 0;
    padding: 0;
}

li {
    list-style: none;
}

ul {
    padding: 0;
    margin: 0;
}

.calendar-container {
    display: grid;
    grid-template-columns: 50px auto;
    grid-template-rows: auto;
    gap: 1px 1px;
    grid-template-areas:
    ". header"
    "timeslots-container main";
    background: #325288;
}

.weekdays,
.daynumbers {
    display: grid;
    grid-template-columns: repeat(7, 1fr);
}

.daynumbers {
    min-height: 1em;
}

.weekdays {
    background: #19456B;
    color: white
}

.header {
    background-color: gainsboro;
    grid-area: header;
}

.timeslots-container {
    background-color: lightgray;
    grid-area: timeslots-container;
    align-items: center;
}

.timeslots {
    display: flex;
    flex-direction: column;
    align-items: center;
}

.timeslots li {
    min-height: 60px;
}

.timeslots li::after {
    content: "";
    position: absolute;
    left: 10px;
    width: 100%;
    height: 1px;
    background: lightgray;
    z-index: 1;
}

.event-container {
    display: grid;
    grid-template-columns: repeat(7, auto);
    grid-template-rows: repeat(48, auto);
    grid-area: main;
    position: relative;
}

.slot {
    position: absolute;
    background: darkcyan;
    border-radius: 5px;
    z-index: 5;
    color: white;
    font-size: 12px;
}

.slot-1 {
    height: 30px;
    grid-row: 106;
    grid-column: 3;
}

Screenshot

enter image description here

Solution

Your issue is with:

.timeslots li::after {
    content: "";
    position: absolute;
    left: 10px;
    width: 100%;
    height: 1px;
    background: lightgray;
    z-index: 1;
}

setting it to left: 10px is a mistake and why its causing your code to look like this, because technically it is taking left: 10px on the entire page. You need to set it so that it does not overlap the li element by setting it to relative so it stays inside.

So I have done a few changes to your css. First I added this css:

.calendar-container {
    overflow: hidden;
}

Then I set the li elements to relative:

.timeslots li {
    position: relative;
}

then I adjusted your li::after css:

.timeslots li::after {
    left: 0px;
    width: 3000px;
}

this should solve your problem since the ::after now stays inside the li and not the entire page, and the overflow: hidden hides any overflow that causes side-scroll.