Blazor Routing Essentials: Mastering URL Parameters and Query Strings
Tags: blazor, development, web
Published: 2024-04-26 04:39:01

---
title: Blazor Routing Essentials: Mastering URL Parameters and Query Strings
published: true
date: 2024-04-23 12:34:17 UTC
tags: blazor, development, web, development
canonical_url: https://www.syncfusion.com/blogs/post/blazor-url-parameters-query-strings
cover_image: https://dev-to-uploads.s3.amazonaws.com/uploads/articles/puwq1ukpp4bvnco63ibg.png
---
**TL;DR:** Query parameters define sorting, pagination, or filter operations and are more readable because they include the keys in the URL. URL parameters are less readable because they don’t, and they are used to define locations of resources or entities. This blog shows how to use URL parameters and query strings in a Blazor app to make it responsive to user input. 

As developers, it is essential to understand how URL parameters and query strings work to get the maximum out of them in Blazor routing. This article will explore the use of URL parameters and query strings using a Blazor application.

## Prerequisites

Before creating the app, you need to have these installed:

- [Visual Studio 2022](https://visualstudio.microsoft.com/vs/ "Visual Studio 2022")
- [.NET SDK 5.0 or later](https://dotnet.microsoft.com/en-us/download/visual-studio-sdks ".NET SDK") (this blog uses .NET 6.0)

## What is a URL parameter?

URL parameters are a way to pass data using the route URL. They are enclosed within curly braces ({}) and separated by forward slashes (/), as shown in the following code example.

```
api/employee/{id}
```

In the example, **{id}** is a URL parameter of the endpoint. It is possible to have multiple URL parameters separated by forward slashes in a single URL. For example, if we need to get employee details using the employee ID and employee type, we can pass multiple parameters, as in the following example.

```
api/employee/{id}/{type}
```

## Using URL parameters in a Blazor app

Let’s create a simple Blazor app to demonstrate how to use URL parameters.

### Step 1: Initialize a new project

First, we need to [create a Blazor app](https://learn.microsoft.com/en-us/aspnet/core/blazor/tooling?view=aspnetcore-8.0&pivots=windows "Tooling for ASP.NET Core Blazor") using Visual Studio. To do this, open Visual Studio and create a new Blazor WebAssembly app called **BlazorRoutingParameters**, as shown in the following image. ![create a new Blazor WebAssembly app](https://www.syncfusion.com/blogs/wp-content/uploads/2024/04/Initialize-a-New-Project.png)

### Step 2: Implement models and services

Create a folder called **Models** inside the root directory. Then, create a model class called **User** inside that folder, **Project/Models/User.cs**, as shown in the following code example.

```csharp
public class User
{
    public int Id { get; set; }
    public string Name { get; set; }
    public int Age { get; set; }
    public string Address { get; set; }
}
```

After creating the **User** model class, we need to create the data access service for the user. To do that, create a folder called **Services** inside the root directory. Then, create the interface called **IUserDataAccessService** inside the **Services** folder **Project/Services/IUserDataAccessService.cs** as in the following code example.

```csharp
public interface IUserDataAccessService
{
    List<User> GetUsers();
}
```

Next, inherit the **IUserDataAccessService** by creating a class called **UserDataAccessService**  **Project/Services/UserDataAccessService.cs**, which implements the **IUserDataAccessService** interface.

```csharp
public class UserDataAccessService : IUserDataAccessService
{
    private User[] users = {new User()
    {
        Id = 1,
        Name = "Samith Patel",
        Address = "London, Uk",
        Age = 27
    },new User()
    {
        Id = 2,
        Name = "Yohan Silva",
        Address = "London, Uk",
        Age = 28
    }};

    public List<User> GetUsers()
    {
        return users.ToList();
    }
}
```

We can observe the implementation of the **IUserDataAccessService** interface and the **GetUsers** method, which returns a list of users. In this example, a predefined user array ( **users** ) is used to return the list of users.

Next, create an interface called **IUserService** inside the Services folder: **Project/Services/IUserService.cs**.

```csharp
public interface IUserService
{
    public User GetUser(int id);
}
```

Then, inherit **IUserService** and implement a new class called **UserService** inside the **Services** folder **Project/Services/UserService.cs**.

```csharp
public class UserService : IUserService
{
    private readonly IUserDataAccessService _userDataAccessService;
    
    public UserService(IUserDataAccessService userDataAccessService)
    {
        _userDataAccessService = userDataAccessService;
    }

    public User GetUser(int id)
    {
        var user = _userDataAccessService.GetUsers().FirstOrDefault(s => s.Id == id);
        return user;
    }
}
```

The previous code injects the **IUserDataAccessService** interface in the constructor of the **UserService,** and the **GetUser** method returns the user details for a specific user by using the ID. The **GetUser** method essentially queries a data source through the injected **\_userDataAccessService** to retrieve user details by filtering for a specific **id**. It employs LINQ to locate the user with the matching **id** efficiently and then returns the user object if found.

### Step 3: Register services

Register all services created in the previous steps using the **program.cs** as in the following code example.

```csharp
builder.Services.AddScoped<IUserDataAccessService, UserDataAccessService>();
builder.Services.AddScoped<IUserService, UserService>();
```

### Step 4: Create a Razor page

Create a Razor page called **FetchURLData** inside the **Pages** folder to display fetched data: **Project/Pages/FetchURLData.razor**.

First, we need to define the route with the URL parameter called **UserId** for this page using the **@page** directive.  This  **UserId** must be an integer.

```csharp
@page "/fetchURLdata/{UserId:int}"
```

This route definition specifies that this page will be accessible at a URL like **/fetchURLdata/1**, where **1** is the **UserId** passed as a URL parameter.

In addition, we need to inject the **IUserService** interface using the **@inject** directive. We will use **IUserService** to get user details using the **UserId**.

```csharp
@inject IUserService _userService;
```

### Step 5: Get the URL Parameter

We have used the **Parameter** attribute for the **UserId** variable. This attribute allows the Razor page to capture the value of **UserId** from the URL and assign it to the **UserId** variable. We also set a default value of **0** for **UserId** if it is not provided in the URL.

```
[Parameter]
public int UserId { get; set; } = 0;
```

Then, the **UserId** variable value is used to get user details.

```csharp
@code {
    private User _user;
    
    [Parameter]
    public int UserId { get; set; } = 0;

    protected override void OnInitialized()
    {
        _user = _userService.GetUser(UserId);
    }
    
}
```

Inside the **@code** block, we declare a private **\_user** variable of type User to store user details. This variable is used to display the user’s information on the page.

We override the **OnInitialized** method, which is part of the Blazor component lifecycle and is called when the component is initialized. In this method, we use the **\_userService** to get user details by passing the UserId value as a parameter.

The **GetUser** method retrieves user details based on the **UserId** provided in the URL.

Finally, we can visualize the user details on the Razor page using HTML elements. The user details are displayed if the **\_user** is not null, and a loading message is shown while the data is being fetched.

```csharp
@page "/fetchURLdata/{UserId:int}"
@inject IUserService _userService;

<PageTitle>User</PageTitle>

<h1>User Details</h1>

<p>This component will show the user details.</p>

@if (_user == null)
{
    <p><em>Loading...</em></p>
}
else
{
    <p >User Id : @_user.Id</p> 
    <p >Name : @_user.Name</p>
    <p >Age : @_user.Age</p>
    <p >Address : @_user.Address</p>
}
```

### Step 6: Set the route path using the navigation bar

Now, create a new Razor page called **NavMenu** inside the **Shared** folder **Project/Shared/NavMenu.razor**. There, update the **href** tag of the **NavLink** as in the following code example.

```xml
<div class="nav-item px-3">
 <NavLink class="nav-link" href="fetchURLdata/1">
  <span class="oi oi-list-rich" aria-hidden="true"></span> Fetch URL data
 </NavLink>
</div>
```

Here, the value **1** is passed as a URL parameter.

```
fetchURLdata/1
```

We can run and test the app to ensure everything is working as expected. We can see that it returns the user data for the **UserId**, which is passed using the URL parameter. ![Run the Blazor WebAssembly app](https://www.syncfusion.com/blogs/wp-content/uploads/2024/04/Set-the-Route-Path-Using-the-Navigation-Bar.png)

## What is the query string?

A query string is a URL section containing data given to a web app or back-end database. Query strings allow the transmission of data (parameters) from one page to another, making them accessible on the receiving page.

```
api/employee? Name=John
```

In the previous example, the query string is separated by a question mark. There is a single query parameter in the URL. It contains a parameter named **name** with the value **John**.

Additionally, it is possible to include multiple query parameters in the URL. However, we need to separate each query string using **&**, as shown in the following code line.

```
api/employee? Name=John&age=20
```

## Using query strings in the Blazor app

We are using the same project for this example as we did for the previous one. Here, we are trying to get user details using the **IUserService** and **IUserDataAccessService** interfaces.

### Step 1: Installing necessary packages

First, we need to [install the NuGet package](https://docs.microsoft.com/en-us/nuget/consume-packages/install-use-packages-visual-studio "Install and manage packages in Visual Studio using the NuGet Package Manager") called the [Microsoft.AspNetCore.WebUtilities 2.2.0](https://www.nuget.org/packages/Microsoft.AspNetCore.WebUtilities/ "Microsoft.AspNetCore.WebUtilities NuGet package"). ![Installing the Microsoft.AspNetCore.WebUtilities 2.2.0 NuGet package](https://www.syncfusion.com/blogs/wp-content/uploads/2024/04/Installing-Necessary-Packages.png)

### Step 2: Creating a new razor page

Next, create a Razor page named **FetchQueryData** inside the **Pages** folder **Project/Pages/FetchQueryData.razor** and follow the next flow.

First, we have defined the route using the **@page** directive in the **FetchQueryData.razor** file. So, we need to add the following code to the **FetchQueryData.razor** file.

```
@page "/fetchquerydata"
```

In addition, the **NavigationManager** class is injected into the page since it is used to access the query string parameter using the URL. So, we need to add the following code to the **FetchQueryData.razor** file.

```
@inject NavigationManager NavManager
```

### Step 3: Extracting query string

Next, import the **Microsoft.AspNetCore.WebUtilities** package to use the **QueryHelpers** class to parse the query string.

```
@using Microsoft.AspNetCore.WebUtilities
```

Then, we can get user details using the **GetUser** method from the **IUserService** interface. In that case, we need to inject the **IUserService** interface into the **FetchQueryData.razor** file.

```
@inject IUserService _userService;
```

The query string values are initially stored as strings, but we can convert them as needed. In this example, the string value is converted to an integer. We can see this conversion in the following code example.

```csharp
protected override void OnInitialized()
{
  var uri = NavManager.ToAbsoluteUri(NavManager.Uri);

  if (QueryHelpers.ParseQuery(uri.Query).TryGetValue("userId", out var userId))
  {
    _userId = Convert.ToInt32(userId);
  }

  _user = _userService.GetUser(_userId);

}
```

Here, we can use the **QueryHelpers** class for implementation. The **QueryHelpers** class is generally used to work with query strings in URLs. It provides methods to encode and decode query string values, helping us properly format and parse URLs for web apps.

The **QueryHelpers** class is used to parse the query string with the **ParseQuery** method, and the **TryGetValue** method is used to get the values of the query string named **userId**. If there is a **userId** keyword in the returned value, it returns true. Otherwise, it returns false. Then, the **GetUser()** method is used to get user details by passing the **UserId** value as a parameter.

We need to visualize the user details. For that, we can use the following HTML code example.

```xml
<PageTitle>User</PageTitle>

<h1>User Details</h1>

<p>This component will show the user details.</p>

@if (_user == null)
{
    <p><em>Loading...</em></p>
}
else
{
    <p >User Id : @_user.Id</p> 
    <p >Name : @_user.Name</p>
    <p >Age : @_user.Age</p><p >Address : @_user.Address</p>
}
```

In this code block, the **\_user** variable is checked for null using the **if-else** statement. We visualize the user data only if it isn’t null.

### Step 4: Setting the route path using the navigation bar

We need to open the Razor page called **NavMenu** inside the **Shared** folder. Next, we modify the **href** attribute of the **NavLink**, as in the following code example.

```xml
<div class="nav-item px-3">
 <NavLink class="nav-link" href="fetchquerydata?userId=1">
  <span class="oi oi-list-rich" aria-hidden="true"></span> Fetch Query data
 </NavLink>
</div>
```

We can then test the app to ensure everything works as expected, and it should return the user data for the **userId** set to 1. ![Run the Blazor app](https://www.syncfusion.com/blogs/wp-content/uploads/2024/04/Setting-the-Route-Path-Using-the-Navigation-Bar-output.png)

## Differences between a URL parameter and query string

- A URL parameter is a part of a URL. It is mainly used to define the location of the resources or entity. However, a query string is not a part of the URL. It is added to the URL by users using a question mark, and it is mostly used to define sorting, pagination, or filter operations.
- The query string can be null, but the URL parameter can’t be null since it’s part of the URL. So, if you don’t append the URL parameter to the URL, you will get a 404 error (Not Found). But you can avoid this issue by using the nullable parameter **(userId:int?)** with the URL parameter.
- Query parameters are more readable because they include the keys in the URL. URL parameters are less readable because they don’t represent or show keys with the URL.

## Keep in mind

When considering security, you should not use these approaches to pass sensitive information like passwords, secrets, or credit card numbers. If you use query parameters to include sensitive information, they may be saved in the browser history. In other words, anyone with access to the browser history may view the URLs that were browsed, as well as any query or URL parameters provided. This means malicious malware can search a user’s browser history for sensitive data.

## Conclusion

This article discussed how to use URL parameters and query strings in a Blazor WebAssembly app and the difference between URL and query parameters. I hope this article was informative. Thank you for reading.

For those interested in exploring the latest version of Essential Studio, it is readily accessible to existing customers via the [License and Downloads](https://www.syncfusion.com/account/downloads "Essential Studio License and Downloads page") page. If you’re not currently a Syncfusion customer, we invite you to experience our 30-day [free trial](https://www.syncfusion.com/downloads "Get the free evaluation of the Essential Studio products"), enabling you to explore all available features.

Should you have any questions or require assistance, please reach out to us through our [support forums](https://www.syncfusion.com/forums "Syncfusion Support Forum"), [support portal](https://support.syncfusion.com/ "Syncfusion Support Portal"), or [feedback portal](https://www.syncfusion.com/feedback/ "Syncfusion Feedback Portal"). We’re dedicated to providing comprehensive support and are always delighted to assist you!

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