IndependentTag.Create

private IndependentTag CreateIndependentTag(Autodesk.Revit.DB.Document document, Wall wall)
{
    // make sure active view is not a 3D view
    Autodesk.Revit.DB.View view = document.ActiveView;

    // define tag mode and tag orientation for new tag
    TagMode tagMode = TagMode.TM_ADDBY_CATEGORY;
    TagOrientation tagorn = TagOrientation.Horizontal;

    // Add the tag to the middle of the wall
    LocationCurve wallLoc = wall.Location as LocationCurve;
    XYZ wallStart = wallLoc.Curve.GetEndPoint(0);
    XYZ wallEnd = wallLoc.Curve.GetEndPoint(1);
    XYZ wallMid = wallLoc.Curve.Evaluate(0.5, true);
    Reference wallRef = new Reference(wall);

    IndependentTag newTag = IndependentTag.Create(document, view.Id,  wallRef, true, tagMode, tagorn, wallMid);
    if (null == newTag)
    {
        throw new Exception("Create IndependentTag Failed.");
    }

    // newTag.TagText is read-only, so we change the Type Mark type parameter to 
    // set the tag text.  The label parameter for the tag family determines
    // what type parameter is used for the tag text.

    WallType type = wall.WallType;

    Parameter foundParameter = type.LookupParameter("Type Mark");
    bool result = foundParameter.Set("Hello");

    // set leader mode free
    // otherwise leader end point move with elbow point

    newTag.LeaderEndCondition = LeaderEndCondition.Free;
    XYZ elbowPnt = wallMid + new XYZ(5.0, 5.0, 0.0);
    newTag.SetLeaderElbow(wallRef, elbowPnt);
    XYZ headerPnt = wallMid + new XYZ(10.0, 10.0, 0.0);
    newTag.TagHeadPosition = headerPnt;

    // change tag orientation to AnyModelDirection
    newTag.TagOrientation = TagOrientation.AnyModelDirection;

    // change tag rotation angle to PI/4
    newTag.RotationAngle = Math.PI / 4;

    return newTag;
}