在项目中需要用到画线功能，要求不同的电压等级使用不同的颜色，如1000 是红色 500是蓝色
不同项目的线可以用 LineString 类描述，上代码
SharpMap.Data.FeatureDataTable dt = new SharpMap.Data.FeatureDataTable();
            dt.Columns.Add("ContainerGrade");
            SharpMap.Data.FeatureDataRow row = dt.NewRow();
            row["ContainerGrade"] = "500";

            LineString lineString = new LineString();
            lineString.Vertices.Add(new SharpMap.Geometries.Point(121.0266, 29.1368));
            lineString.Vertices.Add(new SharpMap.Geometries.Point(120.527, 29.85));

            row.Geometry = lineString;
            dt.AddRow(row);

            VectorLayer SymbolsLayer = new VectorLayer("ProjectLineLayer");
            SharpMap.Rendering.Thematics.CustomTheme theme = new SharpMap.Rendering.Thematics.CustomTheme(GetMyLineStyle);
            SymbolsLayer.DataSource = new Geomet