Sequence-diagram.md

 [Original mermaid-js sequence diagram documentation](https://mermaid-js.github.io/mermaid/#/sequenceDiagram)
 
+A Sequence diagram is an interaction diagram that shows how processes operate with one another and in what order
+
+To create sequence diagram call create new `SequenceDiagramBuilder`. You could enable `autonumber` of sequence steps within its constructor
+```c#
+var builder = new SequenceDiagramBuilder(autoNumber:true);
+```
+
+## Defining members
+```c#
+var alice = diagram.AddMember("Alice", MemberType.Participant);
+var bob = diagram.AddMember("Alice", MemberType.Participant);
+```
+
+### Links
+You could add links for diagram members
+```c#
+alice.AddLink("Dashboard", new Uri("https://dashboard.contoso.com/alice"));
+alice.AddLink("Wiki", new Uri("https://wiki.contoso.com/alice"));
+```
+
+## Building diagram
+### Messages
+To sent message from one member to another/self
+```c#
+builder
+    .Message(alice, bob, "Hello Bob!", MessageType.Solid)
+    .Message(alice, bob, "Hello! Can you hear me?", MessageType.Solid)
+```
+
+For simpler messaging process definition between two members you could use Messaging
+```c#
+builder
+    .Messaging(alice, bob)
+        .Request("Hi Bob!", MessageType.SolidArrow)
+        .Response("Hello Alice!", MessageType.SolidArrow)
+        .Request("How are you?", MessageType.SolidArrow)
+        .Response("Well ..", MessageType.DottedArrow)
+        .Response("Done", MessageType.SolidArrow)
+    .End()
+```
+
+### Activation
+To do things, when some of the members activated use `Activate` method
+```c#
+builder.Activate(alice, diagram =>
+{
+    diagram.Message(alice, bob, "Hello", MessageType.Solid);
+});
+```
+
+### Loops
+```c#
+builder.Loop("Endless conversation", diagram =>
+{
+    diagram.Message(alice, bob, "Hello", MessageType.Solid);
+    ...
+});
+```
+
+### Alt
+It is possible to express alternative paths in a sequence diagram
+```c#
+builder.AltOr(
+    "Alice hungry",
+    diagram => diagram.Message(alice, bob, "Wait Bob, I need something to eat", MessageType.Solid),
+
+    "Alice not hungry",
+    diagram => diagram.Message(alice, bob, "Ok, let`s go", MessageType.Solid)
+);
+```
+
+### Optional
+```c#
+builder.Optional("Alice tired", diagram => ...);
+```
+
+### Parallel
+```c#
+builder.Parallel(new [] {
+("alice is going to work", diagram => ...),
+("alice is talking to the phone", diagram => ...)
+});
+```
+or
+```c#
+builder.Parallel(
+("alice is going to work", diagram => ...),
+("alice is talking to the phone", diagram => ...)
+);
+```
+
+## Rectangles
+It is possible to highlight flows by providing colored background rects.
+```c#
+builder.Rect(Color.Yellow, diagram => ...);
+```
+
+## Notes
+### Note
+```c#
+builder
+    .Note(alice, NoteLocation.LeftOf, "Alice is a girl")
+    .Note(bob, NoteLocation.LeftOf, "Bob is a boy");
+```
+
+### Note over members
+```c#
+builder.NoteOver("Teenagers", alice, bob);
+```
+
+## Generating markdown
+```c#
+string markdownSyntax = builder.Build();
+```
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