如何解决图形未显示在MVC Core中
您好可爱的聪明人,我希望您可以通过我正在做的Graph项目帮助我。我在MVC Core项目中找到了一些漂亮的代码来创建图形here,我正在使用的片段是“数据库中的数据”,在调试时,我可以在视图中看到已成功输入数据库中的值进入ViewBag.DataPoints,但未显示图形。 我在Visual Studio 2019中使用.NET Core 3.1。 我将非常感谢您能提供的任何帮助。 谢谢你一百万。
型号:
public class Point
{
[Key]
public int x { get; set; }
public Nullable<int> y { get; set; }
}
上下文:
public class DataPointsDB : DbContext
{
public DataPointsDB(DbContextOptions<DataPointsDB> options)
: base(options)
{
}
public virtual DbSet<Point> Points { get; set; }
}
控制器:
public class PointsController : Controller
{
private readonly DataPointsDB _db;
public PointsController(DataPointsDB db)
{
_db = db;
}
public IActionResult Index()
{
IEnumerable<Point> objList = _db.Points;
return View(objList);
}
public IActionResult Create()
{
ViewData["x"] = new SelectList(_db.Points,"x","y");
return View();
}
[HttpPost]
[ValidateAntiForgeryToken]
public async Task<IActionResult> Create([Bind("x,y")] Point point)
{
if (ModelState.IsValid)
{
_db.Add(point);
await _db.SaveChangesAsync();
return RedirectToAction(nameof(Index));
}
ViewData["x"] = new SelectList(_db.Points,"y",point.x);
return View(point);
}
// GET: HowTo
public ActionResult DataFromDataBase()
{
try
{
ViewBag.DataPoints = JsonConvert.SerializeObject(_db.Points.ToList(),_jsonSetting);
return View();
}
catch (EntityException)
{
return View("Error");
}
catch (System.Data.sqlClient.sqlException)
{
return View("Error");
}
}
JsonSerializerSettings _jsonSetting = new JsonSerializerSettings() { NullValueHandling = NullValueHandling.Ignore };
}
查看:
@model IEnumerable<Test_Chart.Models.Point>
<div id="chartContainer"></div>
<script type="text/javascript">
var result = @Html.Raw(ViewBag.DataPoints);
var dataPoints =[];
for(var i = 0; i < result.length; i++){
dataPoints.push({label:result[i].x,y:result[i].y});
}
$(function () {
var chart = new CanvasJS.Chart("chartContainer",{
theme: "light2",zoomEnabled: true,animationEnabled: true,title: {
text: "Line Chart with Data-Points from DataBase"
},data: [
{
type: "line",dataPoints: dataPoints,}
]
});
chart.render();
});
</script>
,我已经添加了
{Layout中的<script src="https://canvasjs.com/assets/script/canvasjs.min.js"></script>
再次感谢x
解决方法
供您参考。...
//this is not needed as we not doing anything,if you want the chart to
//happen when the page is loaded then add "renderChart();" inside
//otherwise delete and add onclick to some element with "renderChart();"
$(function () {
//this is short hand for saying when the doc is finished loading... run this.
});
//out side of function so its global,//example: not what I'm suggesting...
// trying to show you the importance of do something when
// we have the data...
var dataPoints =[];
function renderChart1() {
var chart = new CanvasJS.Chart("chartContainer",{
theme: "light2",zoomEnabled: true,animationEnabled: true,title: {
text: "Line Chart with Data-Points from DataBase"
},data: [
{
type: "line",dataPoints: dataPoints,}
]
});
chart.render();
}
//now you can not call renderChart1() as there are no dataPoints so lets fetch them
//https://www.w3schools.com/jquery/jquery_ref_ajax.asp
$.get("http://localhost:64160/DataFromDataBase",function(data){
//when we have the data set it. this is why we made it global
//a little confusing but was trying to show smaller steps
// to get the version below altho i think i my have just made it more confusing
dataPoints = data;
renderChart1();
});
//better version is.... its much easier to understand
//-----------------------------------------------
function renderChart() {
$.get("http://localhost:64160/DataFromDataBase",function(data){
//data could be a more complex object instead of just the dataPoints
var chart = new CanvasJS.Chart("chartContainer",{
theme: "light2",title: {
text: "Line Chart with Data-Points from DataBase"
},data: [{
type: "line",dataPoints: data,}]
});
chart.render();
});
}
//-----------------------------------------------
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