TeeChart being rendered in export in MVC application in image format (eg PNG, JPEG). During simultaneous access duplicate hash id key error is generated.

This occurs in the Canvas paint code and relates to generic limitations of multiple access in GDI+.


The problem  has workarounds. You can turn off use of the cache for improvements.
ie.
Steema.TeeChart.Utils.UseCaches = false;

But the recommended way to use TeeChart as an MVC component, for multiple simultaneous access, is to add a lock around the Chart rendering code.

eg.
==========
private static Object renderLock = new Object();

public void GetChart()
{
  lock (renderLock)
  {
    Steema.TeeChart.Web.WebChart wChart = new Steema.TeeChart.Web.WebChart();

    //Steema.TeeChart.Utils.UseCaches = false;

    wChart.Chart.Series.Add(new Steema.TeeChart.Styles.Line());
    wChart.Chart.Series[0].FillSampleValues();

    tempStream1 = new System.IO.MemoryStream();
    wChart.Chart.Export.Image.PNG.Save(tempStream1);
    tempStream1.Flush();
    Response.ContentType = "Image/PNG";
    Response.OutputStream.Write(tempStream1.ToArray(), 0, (int)tempStream1.Length);

    tempStream1.Close();
  }
}
=======
or
=======
public ActionResult GetHTML5Chart(int? number) {

lock (renderLock)
{
  Steema.TeeChart.Web.WebChart wChart3 = new Steema.TeeChart.Web.WebChart();

  if (number==0)
    wChart3.Chart.Series.Add(new Steema.TeeChart.Styles.Pie());
  else if (number==1)
    wChart3.Chart.Series.Add(new Steema.TeeChart.Styles.Bar());
  else
    wChart3.Chart.Series.Add(new Steema.TeeChart.Styles.Line());
  wChart3.Chart.Series[0].FillSampleValues();

  string[] customCode = new string[] {

          " chart1.applyTheme(\"minimal\");" };

  wChart3.Chart.Export.Image.JScript.CustomCode = customCode;

  tempStream2 = new System.IO.MemoryStream();
  wChart3.Chart.Export.Image.JScript.Width = 900;
  wChart3.Chart.Export.Image.JScript.Height = 300;
  wChart3.Chart.Export.Image.JScript.Save(tempStream2);

  tempStream2.Position = 0;

  System.IO.StreamReader sr = new System.IO.StreamReader(tempStream2);

  return Content(sr.ReadToEnd());
}
==========