C#中选择一个要素类文件并在axMapcontrol中打开，并将文件中的要素保存在FeatureClass中，生成在要素范围之外的均匀分布的随机点并在axMapcontrol上画出来

以下是使用 ArcObjects SDK for .NET 和 C# 实现您所描述的功能的一些示例代码：

// 获取要素类文件路径
string path = @"C:\Data\MyFeatureClass.shp";

// 打开要素类
IFeatureWorkspace featureWorkspace = OpenWorkspace(path) as IFeatureWorkspace;
IFeatureClass featureClass = featureWorkspace.OpenFeatureClass(System.IO.Path.GetFileNameWithoutExtension(path));

// 将要素类添加到地图控件中
IMap map = axMapControl1.Map;
map.AddLayer(featureClass as ILayer);

// 获取要素类的空间参考
ISpatialReference spatialReference = featureClass.ShapeFieldName.GeometryDef.SpatialReference;

// 获取要素类的范围
IEnvelope envelope = featureClass.Extent;

// 创建一个点集合
IPointCollection points = new MultipointClass();

// 生成随机点
int pointCount = 100;
Random random = new Random();
for (int i = 0; i < pointCount; i++)
{
    IPoint point = new PointClass();
    point.SpatialReference = spatialReference;

    // 生成均匀分布的随机点
    point.X = envelope.XMin + (envelope.XMax - envelope.XMin) * random.NextDouble();
    point.Y = envelope.YMin + (envelope.YMax - envelope.YMin) * random.NextDouble();

    // 将点添加到点集合中
    points.AddPoint(point);
}

// 创建要素并添加到要素类中
IFeatureBuffer featureBuffer = featureClass.CreateFeatureBuffer();
featureBuffer.Shape = points as IGeometry;
IFeatureCursor featureCursor = featureClass.Insert(true);
featureCursor.InsertFeature(featureBuffer);
featureCursor.Flush();

// 在地图控件中添加随机点图层
IMultipoint multipoint = points as IMultipoint;
ISimpleMarkerSymbol markerSymbol = new SimpleMarkerSymbolClass();
markerSymbol.Color = GetRGBColor(255, 0, 0); // 设置点的颜色为红色
IMarkerElement markerElement = new MarkerElementClass();
markerElement.Symbol = markerSymbol;
IGraphicsContainer graphicsContainer = axMapControl1.Map as IGraphicsContainer;
IElement element = markerElement as IElement;
element.Geometry = multipoint as IGeometry;
graphicsContainer.AddElement(element, 0);

// 刷新地图控件
axMapControl1.Refresh();

其中，`OpenWorkspace` 方法用于打开 Shapefile 工作空间，代码如下：

public static IWorkspace OpenWorkspace(string path)
{
    IWorkspaceFactory workspaceFactory = new ShapefileWorkspaceFactoryClass();
    return workspaceFactory.OpenFromFile(System.IO.Path.GetDirectoryName(path), 0);
}

`GetRGBColor` 方法用于获取 RGB 颜色，代码如下：

public static IColor GetRGBColor(int r, int g, int b)
{
    IRgbColor color = new RgbColorClass();
    color.Red = r;
    color.Green = g;
    color.Blue = b;
    return color;
}

请注意，上述示例代码仅供参考，您需要根据您的具体需求和数据结构进行修改和调整。