How to collapse/expand Razor components using Blazor syntax? - asp.net-core

Question

I'm currently implementing a form to create a new user along with their respective user rights. In this form, I have about 30 different IT systems and if the user account should have the access rights for that specific IT system, I want to provide a panel to the admin where some extra information must be entered regarding that specific IT system. I want to implement this using razor components. What I have so far is the core view for my "new user form" as well as a razor component for the additional information of a specific IT system. By clicking the + button, I want the component to be visible / expand right below the IT system. That's what It looks like so far:
The new user form:
<div class="row">
<div class="col-sm-2 font-weight-bold">GOODWILL PKW/Smart</div>
<div class="col-sm-2">
<label>Add</label>
<input type="checkbox" />
</div>
<div class="col-sm-2">
<label>Change</label>
<input type="checkbox" />
</div>
<div class="col-sm-2">
<label>Remove</label>
<input type="checkbox" />
</div>
<div class="col-sm-4">
<button #onclick="#collapseGoodwill">+</button>
</div>
</div>
<ModalGoodwillPKW ></ModalGoodwillPKW>
#code {
public void collapseGoodwill() {
}
}
The component:
<div class="panel panel-default border">
<div class="panel-heading alert-primary">
<h3 class="panel-title">Goodwill PKW/smart</h3>
</div>
<div class="panel-body">
<div class="container-fluid">
<div class="row">
<div class="col-sm-2 font-weight-bold">Profile</div>
<div class="col-sm-5">
<input type="checkbox" id="CB_c" />
<label>Salesman</label>
</div>
<div class="col-sm-5">
<input type="checkbox" id="CB_r" />
<label>Administrator</label>
</div>
</div>
</div>
</div>
</div>
Normally, I would use JQuery in the "collapseGoodwill" method to add a .collapse class to this element. But since I am experimenting with Blazor, I'd like to know if there is a 100% Javascript /JQuery free way of doing this.
Thanks!

Answer 1

Within Blazor, you always follow the pattern:
change data
--> new view rendered
Anytime you want to change the component's UI from outside, you should do it by changing the data (model/state/parameter/context/...).
As for this scenario, you can add a Collapsed field to indicate whether the panel itself is collapsed now:
<div class="panel panel-default border #Collapse">
<div class="panel-heading alert-primary">
<h3 class="panel-title">Goodwill PKW/smart</h3>
</div>
<div class="panel-body">
<div class="container-fluid">
<div class="row">
<div class="col-sm-2 font-weight-bold">Profile</div>
<div class="col-sm-5">
<input type="checkbox" id="CB_c" />
<label>Salesman</label>
</div>
<div class="col-sm-5">
<input type="checkbox" id="CB_r" />
<label>Administrator</label>
</div>
</div>
</div>
</div>
</div>
#code{
[Parameter]
public string Collapse{get;set;}="collapse"; // hide by default
}
And whenever you want to collapse it, just set this parameter to collapse:
<div class="row">
<div class="col-sm-2 font-weight-bold">GOODWILL PKW/Smart</div>
<div class="col-sm-2">
<label>Add</label>
<input type="checkbox" />
</div>
<div class="col-sm-2">
<label>Change</label>
<input type="checkbox" />
</div>
<div class="col-sm-2">
<label>Remove</label>
<input type="checkbox" />
</div>
<div class="col-sm-4">
<button #onclick="e => this.Collapsed = !this.Collapsed">
#( this.Collapsed ? "+" : "-")
</button>
</div>
</div>
<ModalGoodwillPKW Collapse="#( this.Collapsed ? "collapse": "")" ></ModalGoodwillPKW>
#code {
private bool Collapsed = true;
}
Demo:
[Edit] : we can even refactor the above code to expose less information by changing the field from string to boolean.
The ModalGoodwillPKW.razor:
<div class="panel panel-default border #(Collapsed? "collapse": "" ) ">
<div class="panel-heading alert-primary">
<h3 class="panel-title">Goodwill PKW/smart</h3>
</div>
...
#code{
[Parameter]
public bool Collapsed{get;set;}= true; // hide by default
}
The UserForm.razor:
<div class="row">
...
<div class="col-sm-4">
<button #onclick="e => this.Collapsed = !this.Collapsed">
#( this.Collapsed ? "+" : "-")
</button>
</div>
</div>
<ModalGoodwillPKW Collapsed="#Collapsed" ></ModalGoodwillPKW>
#code {
private bool Collapsed = true;
}

Answer 2

I had a similar issue, I had a dynamic list of sections that I wanted to collapse, and I couldn't get the bootstrap data-toggle approach to work due to Blazor mis-handling of # anchor tags.
I used the component idea:
<div class="row">
#if (Collapsed)
{
<span #onclick="#Toggle" class="oi oi-plus mr-1"/>
}
else
{
<span #onclick="#Toggle" class="oi oi-minus mr-1"/>
}
#Title
</div>
#if(!Collapsed)
{
#ChildContent
}
#code {
[Parameter]
public RenderFragment ChildContent { get; set; }
[Parameter]
public bool Collapsed { get; set; }
[Parameter]
public string Title { get; set; }
void Toggle()
{
Collapsed = !Collapsed;
}
}
Which I could then use like this:
#foreach (var i in c.Request)
{
<Collapsable Title="#i.SectionName" Collapsed="true">
<ChildContent>
#foreach (var kvp in i.Values)
{
<div class="row">
<div class="col-1"></div>
<div class="col-6 font-weight-bolder">#kvp.Key</div>
<div class="col-5">#kvp.Value</div>
</div>
}
</ChildContent>
</Collapsable>
}
This seems to work well, each section is independently collapsible.
I've not tried it nested though.

Answer 3

Blazor "#Collapse" div with Bootstrap Toggle Button
I took #cjb110 's excellent sample code above and changed it to use a bootstrap badge button as the toggle, which is how I often add more verbose help info to a form field group, by hiding it behind a toggle and using a bootstrap or material info button for if a user wants it.
Component Part
Here's the component part, which you'd probably add to your Blazor solution's Client project's Shared folder as file name Collapsible.razor (note: Blazor component file names are to be capitalized--I think)
<div class="my-1">
<h3>#Title</h3>
#if (Collapsed)
{
<button #onclick="#Toggle" class="badge badge-info mr-2" role="button" >
#ButtonText
</button>
}
else
{
<button #onclick="#Toggle" class="badge badge-info mr-2" role="button" >
#ButtonText
</button>
}
<label>
#LabelText
</label>
</div>
#if(!Collapsed)
{
<div class="card alert alert-info mb-3" role="alert">
#ChildContent
</div>
}
#code {
[Parameter]
public RenderFragment ChildContent { get; set; }
[Parameter]
public bool Collapsed { get; set; }
//input params coming from from page
[Parameter]
public string Title { get; set; }
[Parameter]
public string ButtonText { get; set; }
[Parameter]
public string LabelText { get; set; }
void Toggle()
{
Collapsed = !Collapsed;
}
}
Template Part
I call this the "template" part. You can change the
Title text,
ButtonText,
I use these info-btn toggles typically in forms, so I added a
<label/> tag with LabelText.
In the <ChildContent/> area, in the component file I set it up as a Bootstrap alert class div, so it doesn't require a <p> tag, but put anything in here you want to show up when the toggle is opened.
<Collapsible
Title=""
ButtonText="Info"
LabelText="Search People & Assign Roles: "
Collapsed="true">
<ChildContent>
Find a person, add their role to the product (i.e.: Estimator, Foreman, Customer)
</ChildContent>
</Collapsible>

Answer 4

I was facing issues with the accordion collapse in my project.
This is how I fixed the bootstrap collapse issue in my Blazor app.
I simply copied these dependencies in the index.html file in Blazor webapp and it worked fine.
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.5.2/css/bootstrap.min.css">
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.5.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.16.0/umd/popper.min.js"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.5.2/js/bootstrap.min.js"></script>
Reference: https://www.w3schools.com/bootstrap4/tryit.asp?filename=trybs_collapsible&stacked=h
Let us know if this works for anyone else

Answer 5

There are some long and good answers. I thought I'd come in with the most important punchline, though.
You can hide whatever you want based on C# conditional logic. So you will VERY often use something like:
<div #onclick="()=>IsOpened = !IsOpened">Click on me to show the hidden control.</div>
#if (IsOpened){
<MyHiddenControl />
}
#code {
bool IsOpened;
}