Questions similar to this appear on the MicroStation Programming Forum. This problem appeared in the VBA discussion group.

Q How do I create a shape element using C#?

• My first problem is how to allow an indefinite number of vertices. How do I accumulate datapoints supplied by a user?
• I would like to create a class module to add dynamic "rubber banding" to the place shape command, so a MicroStation user can see the shape being created as they place their points
• How do I repond to the user's reset click to finish capturing points and create a shape?

A Create a class module that inherits the DgnPrimitiveTool interface. Use a member variable to store an elastic array of DPoint3d: GPArray or List<DPoint3d>. A GPArray or List<> knows its size, so you don't have to store the point count in a variable.

With those pieces of data, you have enough information to display rubber banding as the user places datapoints.

Explicit or Implicit Element Creation

A legacy approach, following its MDL ancestry, creates a ShapeElement or LineStringElement explicitly. In the example code, the CreateShapeTool follows that idiom.

A 21^st century approach uses a GPArray to accumulate datapoints. The CreateCurveVectorShapeTool uses that implicit element creation idiom: you just let the DgnPlatformNet classes do the thinking for you. When user indicates she has finished (with a reset), we create a DgnCurveVector from the points. Because we want a closed shape, we set the curve's boundary type to CurveVector.BoundaryType.Outer. Finally we invoke DraftingElementSchema.ToElement to create an element from the DgnCurveVector.

We don't specify an element type, because we don't have to. Those DgnPlatformNet classes do whatever they have to to create an element: in this case a ShapeElement or ComplexShapeElement.

private Element MakeShape(GPArray points, DgnModel model)
{
  DgnCurveVector curves = (DgnCurveVector)points.ToCurveVector();
  curves.SetBoundaryType((int)CurveVector.BoundaryType.Outer);
  return DraftingElementSchema.ToElement(model, curves, null);
}

Create Shape Class

The example CreateShape class uses the DgnPrimitiveTool interface by providing a number of methods that MicroStation calls when certain events happen. Events that are interesting in this example are …

• OnPostInstall, called when the command starts
• OnDataButton, called when the user places a datapoint
• OnDynamicFrame, called as the user moves the cursor
• OnResetButton, called when the user clicks reset

OnPostInstall

Initialise our variables and issue a prompt to the user.

OnDataButton

Store the DPoint3d in our list (List<DPoint3d>) of vertices. There's no need to store the point count, because a List<> knows its own size.

OnDynamicFrame

If the operator has placed the first point, then draw a line from that point to the current cursor position.

If the operator has place more than one point, create a temporary shape from our list of vertices and the current cursor position.

Each time the user moves the mouse, MicroStation calls this subroutine to draw a new element. The element is assigned the active settings.

OnResetButton

Commands

This example provides key-ins to create a line or shape using DgnCurveVector and GPArray, and others to create a legacy shape or line-string …

• CREATE PRIMITIVE LINE
• CREATE PRIMITIVE SHAPE
• CREATE CURVEVECTOR LINE
• CREATE CURVEVECTOR SHAPE

Download the CreateShape Example

The CreateShape C# Project is available in this ZIP file. Unpack the ZIP file and put CreatePrimitive.dll somewhere where MicroStation can find it, such as C:\Program Files\Bentley\MicroStation\mdlapps (or wherever your MS_MDLAPPS configuration variable is pointing).

You can run the sample using the keyin …
mdl load CreatePrimitive

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Other Technologies for MicroStation Developers

Create Shape using MicroStation VBA

See this article about how to create a shape with VBA.

Create Shape using MicroStationAPI

If you're interested in moving from C# to C++, then the MicroStationAPI will help. The MicroStationAPI arrived with MicroStation CONNECT, and is a first-class C++ interface. It's a development and fusion of the MicroStation Development Library (MDL) and the MicroStationAPI provided with the SDK of MicroStation V8i.

See this article about how to create a shape with C++ using the MicroStationAPI.

Questions

Post questions about MicroStation programming to the MicroStation Programming Forum.