@srikanth sankabathula Thanks for posting in Microsoft Q&A. For managing Azure resources, use Azure.ResourceManager namespace and here is .NET SDK reference: Microsoft Azure Resource Manager client library for .NET SDK
However, service limits for subscription are not included in Rest API and hence SDK cannot support it. If you are in need of this feature, feel free to submit feedback via forum and our product team can review and prioritize it. Others can also upvote your ideas.
For service specific, check for namespaces starting with Azure.ResourceManager. in the reference and for example, Azure.ResourceManager.Compute for compute resources (ComputeUsage).
I hope this helps with your question and let us know if any questions.