C#中选择打开一个要素类文件，并将文件中的要素保存在FeatureClass中，生成不在要素类范围内的均匀分布的随机点并在axMapcontrol上画出来

您可以使用ArcObjects中的C#语言开发，具体步骤如下：

1. 使用OpenFileDialog类选择要素类文件，打开并读取其中的要素。

OpenFileDialog openFileDialog = new OpenFileDialog();
openFileDialog.Filter = "Shapefile (*.shp)|*.shp";
if (openFileDialog.ShowDialog() == DialogResult.OK)
{
    string filePath = openFileDialog.FileName;
    IWorkspaceFactory workspaceFactory = new ShapefileWorkspaceFactory();
    IFeatureWorkspace featureWorkspace = (IFeatureWorkspace)workspaceFactory.OpenFromFile(System.IO.Path.GetDirectoryName(filePath), 0);
    IFeatureClass featureClass = featureWorkspace.OpenFeatureClass(System.IO.Path.GetFileNameWithoutExtension(filePath));
    // 读取要素
    IFeatureCursor featureCursor = featureClass.Search(null, false);
    IFeature feature = null;
    while ((feature = featureCursor.NextFeature()) != null)
    {
        // 处理要素
    }
}

2. 使用IRandomGenerator接口生成随机点，并将点加入到一个新的要素类中。

// 生成随机点
IRandomGenerator randomGenerator = new RandomGeneratorClass();
IPoint point = new PointClass();
IPointCollection pointCollection = new MultipointClass();
for (int i = 0; i < 100; i++)
{
    point = new PointClass();
    point.SpatialReference = featureClass.ShapeFieldName.SpatialReference;
    point.X = featureClass.Extent.XMin + (featureClass.Extent.XMax - featureClass.Extent.XMin) * randomGenerator.NextDouble();
    point.Y = featureClass.Extent.YMin + (featureClass.Extent.YMax - featureClass.Extent.YMin) * randomGenerator.NextDouble();
    pointCollection.AddPoint(point);
}

// 创建新的要素类，添加随机点要素
IWorkspaceEdit workspaceEdit = ((IDataset)featureClass).Workspace as IWorkspaceEdit;
if (workspaceEdit != null)
{
    workspaceEdit.StartEditing(false);
    workspaceEdit.StartEditOperation();
    IFeatureClassDescription fcDescription = new FeatureClassDescriptionClass();
    IObjectClassDescription ocDescription = (IObjectClassDescription)fcDescription;
    IFields fields = ocDescription.RequiredFields;
    IFieldsEdit fieldsEdit = (IFieldsEdit)fields;
    IField shapeField = featureClass.Fields.get_Field(featureClass.FindField(featureClass.ShapeFieldName));
    IFieldEdit shapeFieldEdit = (IFieldEdit)shapeField;
    shapeFieldEdit.Name_2 = "SHAPE";
    fieldsEdit.AddField(shapeField);
    IGeometryDef geometryDef = shapeField.GeometryDef;
    IGeometryDefEdit geometryDefEdit = (IGeometryDefEdit)geometryDef;
    geometryDefEdit.GeometryType_2 = esriGeometryType.esriGeometryPoint;
    IFeatureClass newFeatureClass = featureWorkspace.CreateFeatureClass("RandomPoints", fields, ocDescription.InstanceCLSID, ocDescription.ClassExtensionCLSID, esriFeatureType.esriFTSimple, "SHAPE", "");
    for (int i = 0; i < pointCollection.PointCount; i++)
    {
        point = pointCollection.get_Point(i);
        IFeature newFeature = newFeatureClass.CreateFeature();
        newFeature.Shape = point;
        newFeature.Store();
    }
    workspaceEdit.StopEditOperation();
    workspaceEdit.StopEditing(true);
}

3. 在axMapControl中添加新的要素类，并刷新地图。

// 在axMapControl中添加新的要素类
IMap map = axMapControl1.Map;
ILayer layer = new FeatureLayerClass();
layer.Name = "Random Points";
layer.FeatureClass = newFeatureClass;
map.AddLayer(layer);

// 刷新地图
axMapControl1.Refresh();