Failed to evaluate the FilterValue of the Chart

I have one report which has multiple charts and I have to make it dynamic.

Scenario is I have to pass chart name which I have to show using multiple parameters. If I will select one parameter it will show me 1 chart. If I will select two parameters it will show me two charts.

Showing and hiding chart is working fine. but Filters validation is getting failed.

For second chart I put this condition: IIF(Parameters!Task.Count > 1,Parameters!Task.Value(1),"None")

for third I put this condition IIF(Parameters!Task.Count > 2,Parameters!Task.Value(2),"None"

Funny thing is If I am using proper parameter name instead of array values from parameter it is working fine. For hiding property it is working find but while getting values from parameter array as it is multivalued parameter it showing me error

Thanks in advance for replies.

.

Jatinkumar Shah