Kusto nested json coming as null

Question

I am using Application Insights Log-Explorer query window to visualize the below query. Inside the field customDimensions.RemotePC I am string a json payload.

When I try to index the stored json via propery-indexing, i get the value as null. I tried to access it as array that turns null as well.

Could you please help me to access the FirstName property in below diagram.

Answer 1

Try this:

| extend todynamic(tostring(rpc)).FirstName

I believe that the issue is that rpc is string (although it looks as json). Thus you need to "cast" it to dynamic. You first need to tell the compiler though that this is a string value.