Learn To Draw Simple ASP.NET Core Blazor Bar Chart Using Canvas Extensions

If you are new to ASP.NET Core Blazor then check out my other article. Here I have planned to write a series of article. In each article I will explain in detail about how to draw our own chart for ASP.NET Core Blazor Web Application using HTML5 Canvas Blazor Extensions.

In this series we will see one by one in detail starting from:

Dynamic Bar Chart using Blazor Canvas Extentoins
Dynamic Line Chart using Blazor Canvas Extentoins
Dynamic Bar & Line Chart using Blazor Canvas Extentoins
Dynamic Bubble Chart using Blazor Canvas Extentoins

Prerequisites

Create ASP.NET Core Blazor Server Application

After installing all the prerequisites listed above, click Start >> Programs >> Visual Studio 2019 >> Visual Studio 2019 on your desktop. Click New >> Project.

Select Blazor App and click Next button.

Select your project folder and Enter your Project name and then click Create button.

Select Blazor Server App

After creating ASP.NET Core Blazor Server Application, wait for a few seconds. You will see the below structure in solution explorer.

In the Data folder we can add all our Model, DBContext Class, Services and Controller, we will see that in this article.

In the Pages folder we can add all our component files.component file all should have the .razor extension with the file name.

In the Shared folder we can add all left menu form NavMenu.razor file and change the main content from the MainLayout.razor file.

In the _Imports.razor file we can see all set of imports has been added in order to use in all component pages.

In the App.razor file we will add our main component to be displayed by default when run in browser.Appsertings.json can be used to add the connection string.

Startup.cs file is an important file where we add all our endpoints, like Controller end points, HTTP Client, add services and dbcontext to be used in startup Configuration method.

Run to test the application

When we run the application, we can see that the left side has navigation and the right side contains the data. We can see that the default sample pages and menus will be displayed in our Blazor web site. We can use the pages or remove them and start with our own page.

Step 2 Install the Packages

To use the Blazor Canvas Extension in our Blazor Application we need to install the below packages

Blazor.Extensions.Canvas

Right click the solution and click on the Manage Nuget package. Search for all the packages and install all the needed packages like the below image.

After installing the package, we can confirm it from Dependencies Packages.

Note
Add the blazor.extensions.canvas.js File.

Open the _Host.cshtml file and add the below code inside the head tag.

<script src="_content/Blazor.Extensions.Canvas/blazor.extensions.canvas.js"></script>

Step 3 Create Model Class

Next, we need to create the Model class for use in our application for binding the Item name And Item count in the Bar Chart.

Right Click the Data Folder and create new class file as “ItemMaster.cs”

In the class we add the property field name as in the below code.

public String ItemName { get; set; }
public int SaleCount { get; set; }

Creating Service Class

Next we create the ItemMasterService class in order to bind the result in chart with sample Item details with the Item Name and Sale Count per each item. For this we right click on the Data folder and click on Add New Item to add our ItemMasterService class.

In this class we create a method to get the ItemMaster details with sample 5 records of Items with item Name and Sale count per each item as random values.

public class ItemMasterService
{
public Task<ItemMaster[]> GetItemMasters()
{
var rng = new Random();
int ivale = 0;
return Task.FromResult(Enumerable.Range(1, 5).Select(index => new ItemMaster
{
ItemName = "itm" + rng.Next(1, 100),
SaleCount = rng.Next(20, 100),
}).ToArray()); ;
}
}

Step 4 - Add the Service to the Startup.cs

We need to add the services created by us to the Startup.cs ConfigureServices method.

services.AddSingleton<ItemMasterService>();

Step 5 - Working with Client Project

First, we need to add the Razor Component page

Add Razor Component

To add the Razor Component page right click the Pages folder from the Client project. Click on Add >> New Item >> Select Razor Component >> Enter your component name. Here we have given the name as DrawingSample.razor

Note all the component files need to have the extentions as .razor.

In Razor Component Page we have 3 parts of code. First is the iingmport part where we import all the references and models for using in the component, HTML design and data bind part and finally we have the function part to call all the web API to bind in our HTML page and also to perform client-side business logic to be displayed in Component page.

Import part

First, we import all the needed support files and references in our Razor View page. Here we have first imported our Model class to be used in our view and also imported Blazor Canvas Extension for drawing our own chart control for Blazor applications.

@page "/drawingsample"
@using Blazor.Extensions.Canvas
@using Blazor.Extensions;
@using Blazor.Extensions.Canvas.Canvas2D;
@using ClazorCharts.Data
@inject ItemMasterService MasterService

HTML design and data Bind part

Next, we design our DrawingSample details page to display the Bar Chart with item name and Sales count per each item. Here we have added the Blazor Extension Canvaz HTML5 canvas in our Blazor HTML design part for drawing the bar chart.

<h3>Shanu - Draw Bar Chart using Blazor Canvas Extensions</h3>
<hr />
<BECanvas Width="500" Height="500" @ref="_canvasReference"></BECanvas>

Function Part

Function part to get the Service result and bind the result in array and to draw and plot the values for displaying the bar chart.

Here first we declare the ItemsArray to get bind the result of Item Mater in BarChart.

Next we create a string array as pirChartColor to draw each bar with different color from the array.

In OnInitializedAsync we get the ItemMasterService result and bind the result in the ItemsArrys.

In OnAfterRenderAsync Method we draw the Bar Chart using C# draw objects to the Canvas.

@code {
private Canvas2DContext _context;
protected BECanvasComponent _canvasReference;
ItemMaster[] itemsArrys;
private static readonly string[] pirChartColor = new [] {
"#3090C7",
"#BDEDFF",
"#F9B7FF",
"#736AFF",
"#78C7C7",
"#B048B5",
"#4E387E",
"#7FFFD4",
"#3EA99F",
"#EBF4FA",
"#F9B7FF",
"#8BB381",
//"#6CBB3C", "#F87217", "#EAC117", "#EDDA74", "#CD7F32", "#CCFB5D", "#FDD017", "#9DC209", "#E67451", "#728C00","#617C58", "#64E986"
};
protected override async Task OnInitializedAsync() {
itemsArrys = await MasterService.GetItemMasters();
}
protected override async Task OnAfterRenderAsync(bool firstRender) {
int lastend = 0;
int xSpace = 10;
int XvalPosition = xSpace;
int maxDataVal = itemsArrys.Max(row => row.SaleCount);
int widthcalculation = (Convert.ToInt32(_canvasReference.Width) - 100) / itemsArrys.Length;
int chartHeight = Convert.ToInt32(_canvasReference.Height) - 40;
this._context = await this._canvasReference.CreateCanvas2DAsync();
int colorval = 0;
// Draw the axises
await this._context.BeginPathAsync();
await this._context.MoveToAsync(xSpace, xSpace);
// first Draw Y Axis
await this._context.LineToAsync(xSpace, chartHeight);
// Next draw the X-Axis
}
}
}

Conclusion

In this sample we have used a simple method to display the barchart with in 0 to 100 range values. In order to use for any scale, we can find the ratio of each bar and draw the chart. Also we can extend this chart to draw the Legend and other details. As this is our own Chart we can add any functions as per our need.

4 Comments

Join the conversation! Your thoughts help the community grow.

Dave Flood6y ago
Hey Syed. Thanks for your article. I have a problem. Maybe you can help me?I'm displaying a small graph (using the Blazor.Extensions.Canvas) in a column in each row of a (bootstrap) grid. When my grid scrolls the B.E.Canvas components don't move with the row. If I open the browser Dev tools and change the Position property of the B.E.Canvas elements to Absolute, then they scroll as expected, but I can't seem to set this programmatically. Am I just being a dork or is this a limitation with the component?
Sourav Kumar Das6y ago
Nice and useful article Sir.
Amit Mohanty6y ago
Nice article.
Laxmidhar Sahoo6y ago
Sir Thanks for a good article of Blazor