c# 从MySQL往sharpmap中加载矢量数据图层（一）

最近在学习使用开源数据库和开源gis开发库来开发一个简易导航系统，选用了MySQL和sharpmap，但是将矢量图层shapefile导入MySQL之后发现sharpmap 1.1版本不支持将SQL数据直接从MySQL导入，本来想换成支持的postgreSQL，但是一同学习的其他小组否决了，于是探寻从MySQL往sharpmap加载数据的办法。

研究发现，sharpmap原本支持的方法就是通过新建一个map类的实例，然后创建一个VectorLayer类的图层，通过VectorLayer类的方法从系统路径中打开shapefile来加载进入图层中，然后把这个图层加载进入map类中，渲染map类的实例得到一个Image的变量，放在图片控件中显示出来。sharpmap还可以通过通过Extensions类，来从不同的数据源加载图层:

Extension	Are	Cool	Cool
Oracle	Oracle Spatial datasource provider	Data provider	Diego Guidi
PostGIS	PostgreSQL/PostGIS datasource provider	Data provider	Volleyknaller , FObermaier
PostGIS2	PostgreSQL/PostGIS datasource provider	Data provider	Volleyknaller
OGR Provider	Adding support for several vector formats through OGR	Data Provider	Volleyknaller
NetTopologySuite Data Provider	Adds NTS functionality to SharpMap	Data Provider	Diego Guidi
GDAL Raster Layer	Adding support for a vast number of raster image formats using GDAL	Layer	Volleyknaller, FObermaier
SimpleChart	Add pie-charts as symbols to your map based on attribute data	Example	Volleyknaller
SpatiaLite	SQLite/SpatiaLite datasource provider	Data Provider	Bill Dollins,Kev, FObermaier

sharpmap从14年以来就不更新了，据说项目主导者进了公司，对这项目也不上心了，以后估计我都不会用到sharpmap了。
无法从MySQL中直接导入数据，于是采用个折中的办法，从MySQL中储存的记录，构造一张新的shapefile，然后再导入sharpmap中。

上两节讲过如何将shapefile存储进入MySQL中，采用的是GDAL的OGR中的ogr2ogr类，所以想到采用开源的GDAL库来将MySQL表数据写成shapefile文件。找了很久之后没发现c#有直接调用的函数，但是找到了一篇文章例子，改一下就好了。

/******************************************************************************* $Id: createdata.cs 35222 2016-08-28 06:06:11Z goatbar $** Name:     createdata.cs* Project:  GDAL CSharp Interface* Purpose:  A sample app to create a spatial data source and a layer.* Author:   Tamas Szekeres, szekerest@gmail.com******************************************************************************** Copyright (c) 2007, Tamas Szekeres* Copyright (c) 2009-2010, Even Rouault <even dot rouault at mines-paris dot org>** Permission is hereby granted, free of charge, to any person obtaining a* copy of this software and associated documentation files (the "Software"),* to deal in the Software without restriction, including without limitation* the rights to use, copy, modify, merge, publish, distribute, sublicense,* and/or sell copies of the Software, and to permit persons to whom the* Software is furnished to do so, subject to the following conditions:** The above copyright notice and this permission notice shall be included* in all copies or substantial portions of the Software.** THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS* OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER* DEALINGS IN THE SOFTWARE.*****************************************************************************/using System;using OSGeo.OGR;
using OSGeo.OSR;/*** <p>Title: GDAL C# createdata example.</p>* <p>Description: A sample app to create a spatial data source and a layer.</p>* @author Tamas Szekeres (szekerest@gmail.com)* @version 1.0*//// <summary>
/// A C# based sample to create a layer.
/// </summary>
namespace 路径查询程序
{class CreateData{public static void usage(){Console.WriteLine("usage: createdata {data source name} {layername}");System.Environment.Exit(-1);}public static void Main(string[] args){if (args.Length != 2) usage();// Using early initialization of System.ConsoleConsole.WriteLine("");/* -------------------------------------------------------------------- *//*      Register format(s).                                             *//* -------------------------------------------------------------------- */Ogr.RegisterAll();/* -------------------------------------------------------------------- *//*      Get driver                                                      *//* -------------------------------------------------------------------- */Driver drv = Ogr.GetDriverByName("ESRI Shapefile");if (drv == null){Console.WriteLine("Can't get driver.");System.Environment.Exit(-1);}// TODO: drv.name is still unsafe with lazy initialization (Bug 1339)//string DriverName = drv.name;//Console.WriteLine("Using driver " + DriverName);/* -------------------------------------------------------------------- *//*      Creating the datasource                                         *//* -------------------------------------------------------------------- */DataSource ds = drv.CreateDataSource(args[0], new string[] { });if (drv == null){Console.WriteLine("Can't create the datasource.");System.Environment.Exit(-1);}/* -------------------------------------------------------------------- *//*      Creating the layer                                              *//* -------------------------------------------------------------------- */Layer layer;int i;for (i = 0; i < ds.GetLayerCount(); i++){layer = ds.GetLayerByIndex(i);if (layer != null && layer.GetLayerDefn().GetName() == args[1]){Console.WriteLine("Layer already existed. Recreating it.\n");ds.DeleteLayer(i);break;}}layer = ds.CreateLayer(args[1], null, wkbGeometryType.wkbPoint, new string[] { });if (layer == null){Console.WriteLine("Layer creation failed.");System.Environment.Exit(-1);}/* -------------------------------------------------------------------- *//*      Adding attribute fields                                         *//* -------------------------------------------------------------------- */FieldDefn fdefn = new FieldDefn("Name", FieldType.OFTString);fdefn.SetWidth(32);if (layer.CreateField(fdefn, 1) != 0){Console.WriteLine("Creating Name field failed.");System.Environment.Exit(-1);}fdefn = new FieldDefn("IntField", FieldType.OFTInteger);if (layer.CreateField(fdefn, 1) != 0){Console.WriteLine("Creating IntField field failed.");System.Environment.Exit(-1);}fdefn = new FieldDefn("DbleField", FieldType.OFTReal);if (layer.CreateField(fdefn, 1) != 0){Console.WriteLine("Creating DbleField field failed.");System.Environment.Exit(-1);}fdefn = new FieldDefn("DateField", FieldType.OFTDate);if (layer.CreateField(fdefn, 1) != 0){Console.WriteLine("Creating DateField field failed.");System.Environment.Exit(-1);}/* -------------------------------------------------------------------- *//*      Adding features                                                 *//* -------------------------------------------------------------------- */Feature feature = new Feature(layer.GetLayerDefn());feature.SetField("Name", "value");feature.SetField("IntField", (int)123);feature.SetField("DbleField", (double)12.345);feature.SetField("DateField", 2007, 3, 15, 18, 24, 30, 0);Geometry geom = Geometry.CreateFromWkt("POINT(47.0 19.2)");if (feature.SetGeometry(geom) != 0){Console.WriteLine("Failed add geometry to the feature");System.Environment.Exit(-1);}if (layer.CreateFeature(feature) != 0){Console.WriteLine("Failed to create feature in shapefile");System.Environment.Exit(-1);}ReportLayer(layer);}public static void ReportLayer(Layer layer){FeatureDefn def = layer.GetLayerDefn();Console.WriteLine("Layer name: " + def.GetName());Console.WriteLine("Feature Count: " + layer.GetFeatureCount(1));Envelope ext = new Envelope();layer.GetExtent(ext, 1);Console.WriteLine("Extent: " + ext.MinX + "," + ext.MaxX + "," +ext.MinY + "," + ext.MaxY);/* -------------------------------------------------------------------- *//*      Reading the spatial reference                                   *//* -------------------------------------------------------------------- */OSGeo.OSR.SpatialReference sr = layer.GetSpatialRef();string srs_wkt;if (sr != null){sr.ExportToPrettyWkt(out srs_wkt, 1);}elsesrs_wkt = "(unknown)";Console.WriteLine("Layer SRS WKT: " + srs_wkt);/* -------------------------------------------------------------------- *//*      Reading the fields                                              *//* -------------------------------------------------------------------- */Console.WriteLine("Field definition:");for (int iAttr = 0; iAttr < def.GetFieldCount(); iAttr++){FieldDefn fdef = def.GetFieldDefn(iAttr);Console.WriteLine(fdef.GetNameRef() + ": " +fdef.GetFieldTypeName(fdef.GetFieldType()) + " (" +fdef.GetWidth() + "." +fdef.GetPrecision() + ")");}/* -------------------------------------------------------------------- *//*      Reading the shapes                                              *//* -------------------------------------------------------------------- */Console.WriteLine("");Feature feat;while ((feat = layer.GetNextFeature()) != null){ReportFeature(feat, def);feat.Dispose();}}public static void ReportFeature(Feature feat, FeatureDefn def){Console.WriteLine("Feature(" + def.GetName() + "): " + feat.GetFID());for (int iField = 0; iField < feat.GetFieldCount(); iField++){FieldDefn fdef = def.GetFieldDefn(iField);Console.Write(fdef.GetNameRef() + " (" +fdef.GetFieldTypeName(fdef.GetFieldType()) + ") = ");if (feat.IsFieldSet(iField))Console.WriteLine(feat.GetFieldAsString(iField));elseConsole.WriteLine("(null)");}if (feat.GetStyleString() != null)Console.WriteLine("  Style = " + feat.GetStyleString());Geometry geom = feat.GetGeometryRef();if (geom != null)Console.WriteLine("  " + geom.GetGeometryName() +"(" + geom.GetGeometryType() + ")");Envelope env = new Envelope();geom.GetEnvelope(env);Console.WriteLine("   ENVELOPE: " + env.MinX + "," + env.MaxX + "," +env.MinY + "," + env.MaxY);string geom_wkt;geom.ExportToWkt(out geom_wkt);Console.WriteLine("  " + geom_wkt);Console.WriteLine("");}}
}

但是生成的shapefile文件的编码值为(87, ‘0x57’)，所以如果属性表内的值有中文，会乱码。还没找到更改办法。

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c# 从MySQL往sharpmap中加载矢量数据图层（一）

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