SolidWorks API Patterns

Getting Active Document

var swApp = (ISldWorks)Application; var model = swApp.ActiveDoc as IModelDoc2; if (model == null) return; // Always null-check

Traversing Features

var feat = model.FirstFeature() as IFeature; while (feat != null) { // Process feature... feat = feat.GetNextFeature() as IFeature; }

Safe Array Handling

public static List<T> SafeCast<T>(object swArray) where T : class { if (swArray == null) return new List<T>(); return ((object[])swArray).Cast<T>().ToList(); }

// Usage: var bodies = SafeCast<IBody2>(swPart.GetBodies2((int)swBodyType_e.swSolidBody, true));

Getting Bodies from Part

var swPart = model as IPartDoc; if (swPart == null) return;

var bodiesRaw = swPart.GetBodies2((int)swBodyType_e.swSolidBody, true); if (bodiesRaw == null) return;

var bodies = ((object[])bodiesRaw).Cast<IBody2>().ToList(); foreach (var body in bodies) { // Process body... }

Getting Faces from Body

var facesRaw = body.GetFaces(); if (facesRaw == null) continue;

var faces = ((object[])facesRaw).Cast<IFace2>().ToList(); foreach (var face in faces) { var surface = face.GetSurface() as ISurface; if (surface == null) continue;

if (surface.IsCylinder())
{
    // Handle cylindrical face
}
else if (surface.IsPlane())
{
    // Handle planar face
}

}

Reading Custom Properties

var ext = model.Extension; var mgr = ext.CustomPropertyManager[""]; // "" = active config, or config name

string valOut, resolvedValOut; bool wasResolved; int result = mgr.Get5("PropertyName", false, out valOut, out resolvedValOut, out wasResolved);

if (result == (int)swCustomInfoGetResult_e.swCustomInfoGetResult_ResolvedValue) { // Use resolvedValOut }

Writing Custom Properties

var mgr = model.Extension.CustomPropertyManager[""];

// Add or update int result = mgr.Add3( "PropertyName", (int)swCustomInfoType_e.swCustomInfoText, "PropertyValue", (int)swCustomPropertyAddOption_e.swCustomPropertyDeleteAndAdd );

Assembly Traversal

var swAssy = model as IAssemblyDoc; if (swAssy == null) return;

var compsRaw = swAssy.GetComponents(true); // true = top-level only if (compsRaw == null) return;

var components = ((object[])compsRaw).Cast<IComponent2>().ToList(); foreach (var comp in components) { if (comp.IsSuppressed()) continue;

var compModel = comp.GetModelDoc2() as IModelDoc2;
if (compModel == null) continue;

// Process component...

}

Selection Manager Pattern

var selMgr = model.SelectionManager as ISelectionMgr; int count = selMgr.GetSelectedObjectCount2(-1);

for (int i = 1; i <= count; i++) // 1-based! { var selType = (swSelectType_e)selMgr.GetSelectedObjectType3(i, -1); var obj = selMgr.GetSelectedObject6(i, -1);

if (selType == swSelectType_e.swSelFACES)
{
    var face = obj as IFace2;
    // Process face...
}

}

Selecting Entities Programmatically

// Select by name (features, planes, etc.) bool success = model.Extension.SelectByID2( "Top", // Name "PLANE", // Type string 0, 0, 0, // X, Y, Z (for point selection) false, // Append to selection 0, // Mark null, // Callout (int)swSelectOption_e.swSelectOptionDefault );

// Select entity directly var selData = selMgr.CreateSelectData(); selData.Mark = 1; bool selected = ((IEntity)face).Select4(true, selData);

Bounding Box

var box = (double[])body.GetBodyBox(); if (box != null && box.Length == 6) { double xMin = box[0], yMin = box[1], zMin = box[2]; double xMax = box[3], yMax = box[4], zMax = box[5];

double length = xMax - xMin;
double width = yMax - yMin;
double height = zMax - zMin;

}

Math Transform (Component Position)

var transform = comp.Transform2 as IMathTransform; if (transform != null) { var arrayData = (double[])transform.ArrayData; // arrayData contains 16 elements: 3x3 rotation + translation + scale double x = arrayData[9]; double y = arrayData[10]; double z = arrayData[11]; }

Error Handling Pattern

public void ProcessPart(IModelDoc2 model) { ErrorHandler.PushCallStack("ProcessPart"); try { // Your code here... } catch (Exception ex) { ErrorHandler.HandleError("ProcessPart", ex.Message, ex); } finally { ErrorHandler.PopCallStack(); } }

Common Gotchas

Gotcha Solution

GetBodies2 returns null not empty array Always null-check before casting

CustomPropertyManager("")

Use indexer: CustomPropertyManager[""]

Enum params need (int) cast (int)swBodyType_e.swSolidBody

GetType() returns int, not enum Cast: (swDocumentTypes_e)model.GetType()

Feature names may be localized Don't hardcode "Cut-Extrude1"

SelectByID2 returns bool Check return value for success

Suppress state affects API calls Check IComponent2.IsSuppressed()

Lightweight components return null Call ResolveAllLightweightComponents() first

Interface casting Use as keyword: model as IPartDoc (returns null if wrong type)

COM lifetime Don't call Marshal.ReleaseComObject

• let COM handle it

Threading All SW API calls must be on main STA thread