数据存储区从变量设置属性名称

I have an unknown variable that I want to use as a datastore property name. I'm using Expando, as I know you can dynamically create properties without first declaring them in the db class, however I am unable to do this as the property names are not known. I get the error: 'StoreNames' object does not support item assignment. Is there any way around this?I have an unknown variable that I want to use a