/// <summary>
/// Creates WorkItem, create a comment and add to the Comments property. Then add the WorkItem to the DbContext
/// </summary>
/// <param name="wiContext"></param>
/// <returns></returns>
private static async Task GenerateWorkItemWithComment2(WorkItemDbContext wiContext)
{
var workItem = new WorkItem
{
Id = Guid.NewGuid(),
Title = "Some work item"
};
var comment = new WorkItemComment
{
Id = Guid.NewGuid(),
Comment = "Some comment",
};
workItem.Comments.Add(comment);
// Add workitem to DbSet with comments
wiContext.WorkItems.Add(workItem);
// WORKS: Generates two inserts
await wiContext.SaveChangesAsync();
var saved = await GetWorkItem(wiContext, workItem.Id);
if (saved.Comments.Count != 1)
{
throw new InvalidOperationException("WorkItem should have one comment");
}
}
static async Task Main(string[] args)
{
using var wiContext = new WorkItemDbContext();
await wiContext.Database.MigrateAsync();
// This will fail.
await GenerateWorkItemWithComment1(wiContext);
// This works
await GenerateWorkItemWithComment2(wiContext);
// This fails
await GenerateWorkItemWithComment3(wiContext);
}
/// <summary>
/// Simulates a disconnected scenario - Creates a work item in a dbContext. Then uses a different Context, loads the WorkItem
/// and tries to add a comment to the Comments property.
/// </summary>
/// <param name="wiContext"></param>
private static async Task GenerateWorkItemWithComment3(WorkItemDbContext wiContext)
{
var workItem = new WorkItem
{
Id = Guid.NewGuid(),
Title = "Some work item"
};
// Save the workItem first with the passed in DbContext
// Like a request to an endpoint "CreateWorkItem"
wiContext.WorkItems.Add(workItem);
await wiContext.SaveChangesAsync();
// simulates a "disconnected scenario" where I only want to add a comment
// Like a request to an endpoint "AddComment"
using (var newContext = new WorkItemDbContext())
{
var existingWorkItem = await newContext.WorkItems.Include(wi => wi.Comments)
.FirstAsync(wi => wi.Id == workItem.Id);
var comment = new WorkItemComment
{
Id = Guid.NewGuid(),
Comment = "SOme comment",
};
existingWorkItem.Comments.Add(comment);
// State is "Unchanged"
var workItemState = newContext.Entry(existingWorkItem).State;
// State is "Detached"
var state2 = newContext.Entry(comment).State;
// Fails
await newContext.SaveChangesAsync();
}
var saved = await GetWorkItem(wiContext, workItem.Id);
if (saved.Comments.Count != 1)
{
throw new InvalidOperationException("WorkItem should have one comment");
}
}
/// <summary>
/// Creates/Saves the WorkItem first then use the same instance and add a comment to the Comments property
/// </summary>
/// <param name="wiContext"></param>
/// <returns></returns>
private static async Task GenerateWorkItemWithComment1(WorkItemDbContext wiContext)
{
var workItem = new WorkItem
{
Id = Guid.NewGuid(),
Title = "Some work item"
};
// Save the workItem first
wiContext.WorkItems.Add(workItem);
await wiContext.SaveChangesAsync();
var comment = new WorkItemComment
{
Id = Guid.NewGuid(),
Comment = "Some comment",
};
// Add the comment to the saved comment instance
workItem.Comments.Add(comment);
// State is unchanged
var workItemState = wiContext.Entry(workItem).State;
// PROBLEM: The comment has a state of Modified.
var state2 = wiContext.Entry(comment).State;
// Call fails with UPDATE comment instead of insert
await wiContext.SaveChangesAsync();
var saved = await GetWorkItem(wiContext, workItem.Id);
if (saved.Comments.Count != 1)
{
throw new InvalidOperationException("WorkItem should have one comment");
}
}
private static Task <WorkItem> GetWorkItem(WorkItemDbContext wiContext, Guid id)
{
return(wiContext.WorkItems.Include(c => c.Comments)
.FirstOrDefaultAsync(wi => wi.Id == id));
}