SetField value doesn't update the actual value.

## Expected behavior
calling Issue.SetField("FieldName", "FieldValue") change the issue field.

## Actual behavior
calling Issue.SetField("FieldName", "FieldValue") doesn't change the issue field

## Steps to reproduce the behavior
//string request is my valid request string
var task = await service.GetIssues(request).ConfigureAwait(continueOnCapturedContext: false);
var issue = task.Result.First();
issue.SetField("State", "Test");
issue.SetField("Product Value", "Nice to Have");

// var filed = issue.GetField("State");
// return right value for specified fields, but actually I am not able to see these changed on YouTrack board, I am using YouTrack //admin user for connection.