Tips on incorporating live data into charts using MVC?

Question

Tips on incorporating live data into charts using MVC?

Recently I started working with ASP.NET MVC on my own project and have encountered some difficulties. One particular challenge I am facing is how to create a line chart using data from a database.

Let me explain the issue in more detail:

Within my database, I have a table that stores information about different metals. When I select a specific metal, I want to display a chart illustrating its price trend over time.

For instance, if I select Copper:

The controller for handling this functionality is PricePoint; but which action should I trigger here?

<a href="@Url.Action("DrawChart", "PricePoint", new { id = item.ID })">@Html.DisplayFor(modelItem => item.name)</a>

By calling the DrawChart Action in the PricePoint controller:

public ActionResult DrawChart()
{
    return View();
}

In the same controller, I have also set up an action to retrieve data from the database, encode it as JSON, and pass it back:

 public ActionResult Statistics(int ?id) {
        // fetching data from database to stats 
        return Json(stats,JsonRequestBehavior.AllowGet);
    }

This relates to my view page where I intend to showcase the chart, within the DrawChart.cshtml file.

<script type="text/javascript">
    $.get('@Url.Action("Statistics")', function(result){
        new Morris.Line({
            element: 'myfirstchart',
            data: [
             result
            ],
            xkey: 'year',
            ykeys: ['value'],
            labels: ['Value']
        });
    });
</script>

My understanding is that upon clicking on a metal, the DrawChart action will render the DrawChart.cshtml view, following which the JavaScript function will invoke the Statistics method to populate data for the chart. Am I on the right track?

However, when accessing the URL http://localhost:50101/PricePoint/DrawChart, I end up with a blank page. On the other hand, requesting http://localhost:50101/PricePoint/Statistics displays json data retrieved from the database.

I'm unsure what could be causing this issue. Interestingly, when I manually input sample data in the script like so:

data: [
      { year: '2008', value: 20 },
      { year: '2009', value: 10 },
      { year: '2010', value: 5 },
      { year: '2011', value: 5 },
      { year: '2012', value: 20 }
    ],

The line chart appears as expected. Apologies for any language barriers, and I appreciate any assistance you can provide in addressing this matter.

javascript asp.net json asp.net-mvc asp.net-mvc-4

Answer 1

Answer №1

I experimented with it and successfully displayed the chart. Here are a few things to consider that may be causing issues:

1) Ensure that your call to

$.get('@Url.Action("Statistics")'

includes an id parameter, even though you have declared it in your action

public ActionResult Statistics(int ?id)

. It's possible that not passing an id is affecting the logic of your database retrieval.

2) I noticed that the link to the DrawChart action included new { id = item.ID }, but this parameter is not captured server-side since the DrawChart action is missing the parameter specification:

public ActionResult DrawChart(id)

. This discrepancy may impact the functionality.

3) Pay attention to what you are returning from the MVC action. The stats object in

return Json(stats,JsonRequestBehavior.AllowGet);

should be a C# array containing value and year properties for each object. Check that your JSON return follows this structure.

If you need to return a string instead of a serialized collection, use something like:

return Content(dataString, "application/json");

4) Make sure that the JSON returned contains properties named year and value, matching the declaration in your Morris object on the xkey and ykey values. JavaScript tends to use lowercase while .NET typically uses uppercase for property names.

Conclusion: I resolved the issue by updating my Statistics method as follows:

 public ActionResult Statistics(int ?id) {
       var data = new[] {new Entry() {value = 20, year = 2008}, new Entry() {value = 10, year = 2009}};

            return Json(data,JsonRequestBehavior.AllowGet);
    }

In your Morris initialization code, remove the array brackets from the data declaration to data : result instead of data : [result]

To troubleshoot further, inspect the output of your Statistics method using Chrome Developer Tools or similar tools. Ensure that the data format matches Morris' expectations to avoid errors.

Remember to wrap the Morris init code in a $(document).ready() function for optimal performance.

Answer 2

I experimented with it and successfully displayed the chart. Here are a few things to consider that may be causing issues:

1) Ensure that your call to

$.get('@Url.Action("Statistics")'

includes an id parameter, even though you have declared it in your action

public ActionResult Statistics(int ?id)

. It's possible that not passing an id is affecting the logic of your database retrieval.

2) I noticed that the link to the DrawChart action included new { id = item.ID }, but this parameter is not captured server-side since the DrawChart action is missing the parameter specification:

public ActionResult DrawChart(id)

. This discrepancy may impact the functionality.

3) Pay attention to what you are returning from the MVC action. The stats object in

return Json(stats,JsonRequestBehavior.AllowGet);

should be a C# array containing value and year properties for each object. Check that your JSON return follows this structure.

If you need to return a string instead of a serialized collection, use something like:

return Content(dataString, "application/json");

4) Make sure that the JSON returned contains properties named year and value, matching the declaration in your Morris object on the xkey and ykey values. JavaScript tends to use lowercase while .NET typically uses uppercase for property names.

Conclusion: I resolved the issue by updating my Statistics method as follows:

 public ActionResult Statistics(int ?id) {
       var data = new[] {new Entry() {value = 20, year = 2008}, new Entry() {value = 10, year = 2009}};

            return Json(data,JsonRequestBehavior.AllowGet);
    }

In your Morris initialization code, remove the array brackets from the data declaration to data : result instead of data : [result]

To troubleshoot further, inspect the output of your Statistics method using Chrome Developer Tools or similar tools. Ensure that the data format matches Morris' expectations to avoid errors.

Remember to wrap the Morris init code in a $(document).ready() function for optimal performance.

Answer 3

Answer №2

When transmitting data (including values and dates) manually from a function, everything works fine. The JSON file is correctly populated, and the chart is displayed as expected. However, when the data is sent from the database, although the JSON file seems to be populated, the chart does not appear.

Below is the code snippet:

public class YearlyStat
    {
        public string year { get; set; }
        public double value { get; set; }
    }

public ActionResult Statistics(int? id)
    {
        var items = from item in db.pricepoints
                    where (item.commodityID == id)
                    select item;

        var stats = new List<YearlyStat>();

        foreach (var item in items)
        {
            stats.Add(new YearlyStat
            {
                year = item.date_of_price.ToShortDateString(),
                value = item.value
            });

        }

        return Json(stats, JsonRequestBehavior.AllowGet);
    }

In both cases, the types being used are string and double...

Answer 4

When transmitting data (including values and dates) manually from a function, everything works fine. The JSON file is correctly populated, and the chart is displayed as expected. However, when the data is sent from the database, although the JSON file seems to be populated, the chart does not appear.

Below is the code snippet:

public class YearlyStat
    {
        public string year { get; set; }
        public double value { get; set; }
    }

public ActionResult Statistics(int? id)
    {
        var items = from item in db.pricepoints
                    where (item.commodityID == id)
                    select item;

        var stats = new List<YearlyStat>();

        foreach (var item in items)
        {
            stats.Add(new YearlyStat
            {
                year = item.date_of_price.ToShortDateString(),
                value = item.value
            });

        }

        return Json(stats, JsonRequestBehavior.AllowGet);
    }

In both cases, the types being used are string and double...

Tips on incorporating live data into charts using MVC?

Answer №1

Answer №2

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