In this post, we will discuss about blazor data binding in depth. This is first part of “Blazor Data Binding in Depth” article.
Introduction
Blazoris a .NET framework for building single-page applications (SPA) using C#, Razor and HTML. Data binding is one the most powerful features of any single-page application through which page UI updates with model data without page reload. We will discuss about data binding feature in Blazor.
This article is part of our step-by-step Blazor series. If you have not read our previous articles on Blazor, you can check them here.
Data Binding in Blazor is a powerful feature that allows us to synchronize a variable and a html element or a component. In simple terms, whenever a variable/property data gets update in C#, UI immediately gets update with updated data and vice-versa. Let’s see data binding types in detail.
One-Way Binding
In one-way binding, data flows in one direction only from C# code to UI. That means any property or variable in C# code directly can be used inside html and whenever this property or variable value gets update in C#, this is immediately updated in UI. However vice-versa in one-way binding is not possible. This is just to display updated model data in the UI.
Let’s understand it with the help of code example. In the following example, take a look at Counter component (counter.razor) that comes with default blazor template project.
In the above code, we have a private variable _currentCount _which is initially set to 0 that displays 0 in paragraph when application runs. The _currentCount _variable works as a one-way binding here. In order to bind one-way values, we use @ symbol followed by variable or property name.
A method IncrementCount is also given in the code which works as an event handler of _onclick _blazor event of button element. When _ClickMe _button will be clicked, handler will be executed and increases the _currentCount _value by one, which will immediately update the UI. Executing event handlers in blazor triggers a re-render which updates the UI.
You are aware now with one-way binding that updates the value in one direction only. What, if you want user to update the variable or property value from UI also. This is where two-way binding comes place.
Before understanding two-way binding in blazor, let’s understand “what are components parameters in blazor?“
[Parameter] attribute in Component
A component can receive data from its parent component using [Parameter] attribute. Any of following types of data can be send to a component through [Parameter] attribute. Methods can also be send thru parameters.
- Data
- Events
- Razor Content
As we saw in our previous article A deep dive on Blazor components that blazor components can be nested. That means a blazor component can be nested inside other blazor components. As an example, let’s create a new component called CounterValueDisplay.razor and nest it inside count component.
So [Parameter] attribute is used when you want to pass any data from parent (Counter) to child (CounterValueDisplay) component.
In above example, Parent (count) component is passing value to Child (CounterValueDisplay) component using [Parameter] attribute. Follow below steps for clear understanding
#blazor #asp.net core #blazor #component parameters in blazor #one-way data binding in blazor #two-way data binding in blazor
