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RadHtmlChart with DateTime Axis Loads Slowly

Problem

The RadHtmlChart performance suffers, or the browser hangs, when using a DateTime Axis with data-points in the same day.

Description

When I use a DateTime Axis, I sometimes see the RadHtmlChart load very slowly, or even cause the browser to hang. This seems to happen when there are data-points that are in the same day, but not when the data-points are more spread out.

Solution

This issue occurs due to the way intervals are automatically generated for a DateTime Axis. The RadHtmlChart looks at the source data to calculate the interval between all data-points along the axis. For example, if the data contain two records that are 5-minutes apart, the data-points on the axis will have an interval of 5-minutes. If the data also contains records spanning a week, over 2,000 data-points would need to be generated along the DateTime Axis to show an unbiased representation of the data.

There are several options to overcome this behavior:

  • Explicitly set the BaseUnit property of the DateTime Axis to a value that will display the data correctly, without producing too many axis data-points.

  • Pre-process the source data before binding to the RadHtmlChart in order to aggregate values that are close together.

  • Remove the Time component from DateTime objects in the source data. This effectively makes the minimum interval one day.

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