Fix JSONDemo.cs - Casting error

[Knicker]

Fix casting error "The binary operator Equal is not defined for the types 'System.Text.Json.JsonElement' and 'System.String'."

It's done in the github editor

[Knicker]

@microsoft-github-policy-service agree

[whuanle]

Your code seems to have some issues and needs to be corrected:

JsonValueKind.Number => property.Value.TryGetInt64(out var l) ?  l: property.Value.GetDouble(),