Accessing Atlassian Jira from a .NET application can be done very easily by installing the Atlassian Jira SDK.
From the nuget console.
This introduces the Jira assembly with alot of different classes and helper functions. E.g. one can connect to Jira using:
Jira.CreateRestClient(url, username, password)
which instantiates the Jira class which can be used to get Versions, Issues, etc. from Jira. A real treat using this library is that it proved Async methods, i.e. await keyword can be used throughout the usage.
getting all Versions of a specific project/key can be done using:
var results = await jiraConn.Versions.GetVersionsAsync(key)
getting issues using a specific JQL query can be done using:
var results = await jiraConn.Issues.GetIssuesFromJqlAsync(jql)