如何在vb.net中使用单个数据表创建多条折线图

Question

I am working on vb.net application where i have to create a multi line chart. The table coming from the database using storing procedure is:-

TagName   On   Off   Trip
  P1      0     0     1
  P2      0     1     1
  P3      0     1     0
  Q1      0     1     0
  Q2      1     0     1
  Q3      2     2     2
  W1      4     2     1
  W2      2     0     1
  W3      1     1     0
  W4      0     1     1
  W5      2     1     1

And the code in vb.net i used to bind the chart named "chTrend" is:-

ds = ObjTags.GetTrendData()
If (ds.Tables(0).Rows.Count > 0) Then

    dt = ds.Tables(0)
    chTrend.DataSource = dt
    chTrend.Series(0).XValueMember = "TagName"
    chTrend.Series(0).YValueMembers = "On"

    chTrend.Series(1).XValueMember = "TagName"
    chTrend.Series(1).YValueMembers = "Off"

    chTrend.Series(1).XValueMember = "TagName"
    chTrend.Series(1).YValueMembers = "Trip"

    For i = 0 To 2
       chTrend.Series(i).ChartType = SeriesChartType.Line
       chTrend.Series(i).IsVisibleInLegend = True
       chTrend.Series(i).IsValueShownAsLabel = True
       chTrend.Series(i).ToolTip = "Data Point Y Value #VALY{G}"
       chTrend.Series(i).BorderWidth = 3
    Next
End If

When i run the program a Error is coming as following

"Index was out of range. Must be non-negative and less than the size of the collection.Parameter name: index"

At the position

chTrend.Series(0).XValueMember = "TagName"

how to solve this?

Answer 1

Assuming that your DataTable only has the four DataColumns {TagName, On. Off. Trip}, then replace everything in your shown code below the line:

chTrend.DataSource = dt

with this.

chTrend.Series.Clear() ' clears any existing series
Dim s As Series
For columnIndex As Int32 = 1 To dt.Columns.Count - 1
    Dim name As String = dt.Columns(columnIndex).ColumnName
    s = chTrend.Series.Add(name)
    s.XValueMember = dt.Columns(0).ColumnName
    s.YValueMembers = name
    s.ChartType = SeriesChartType.Line
    s.IsVisibleInLegend = True
    s.IsValueShownAsLabel = True
    s.ToolTip = "Data Point Y Value #VALY{G}"
    s.BorderWidth = 3
Next
chTrend.DataBind() ' loads the data from dt to the chart

The Chart databinding is a not a binding in the normal sense of binding. You need to tell the chart to copy the data from the source so that it has something to plot. That is what the DataBind method does.