Gdal reads and writes vector files -- C #

When using OGR in C # To Read and Write Vector Data, you must reference "using osgeo. OGR ;". At the same time, in order to process the Chinese path and the Chinese field, you need to set the following two attributes at the beginning, the Code is as follows:

// To support the Chinese path, add the following code (not required in most cases) // osgeo. gdal. gdal. setconfigoption ("gdal_filename_is_utf8", "no"); // to make the Attribute Table field support Chinese characters, add the following osgeo statement. gdal. gdal. setconfigoption ("shape_encoding ","");

1. Read Vector

Read the vector Code as follows, as shown in result 1. The post-processing result 2 is filtered by attribute.

Static void readvectorfile () {// to support Chinese paths, add the following code osgeo. gdal. gdal. setconfigoption ("gdal_filename_is_utf8", "no"); // to make the Attribute Table field support Chinese characters, add the following osgeo statement. gdal. gdal. setconfigoption ("shape_encoding", ""); string strvectorfile = "E: \ datum \ gdalcstest \ debug \ Beijing. SHP "; // register all drivers. registerall (); // open the data datasource DS = OGR. open (strvectorfile, 0); If (DS = NULL) {console. writeline ("opening file [{0}] failed! ", Strvectorfile); return;} console. writeline (" opening file [{0}] successful! ", Strvectorfile); // obtain the number of layers in the data source. Generally, there is only one SHP data layer. If it is MDB or DXF, there will be multiple int ilayercount = Ds. getlayercount (); // obtain the first layer Layer olayer = Ds. getlayerbyindex (0); If (olayer = NULL) {console. writeline ("failed to get layer {0! \ N ", 0); return;} // initializes the layer. If a filtering operation is performed on the layer, all the previous filtering operations are cleared. resetreading (); // filter the elements in the layer using the SQL statement of the attribute table. For details, refer to the SQL query section olayer. setattributefilter ("\" name99 \ "like \" Beijing Municipal District \ ""); // filter the elements in the layer using the specified geometric object // olayer. setspatialfilter (); // filter the elements in the layer by the specified four to the range. // olayer. setspatialfilterrect (); // obtain the Attribute Table header in the layer and output the console. writeline ("attribute table structure information:"); featuredefn odefn = olayer. getlayerdefn (); int ifieldcount = Odefn. getfieldcount (); For (INT iattr = 0; iattr <ifieldcount; iattr ++) {fielddefn ofield = odefn. getfielddefn (iattr); console. writeline ("{0 }:{ 1} ({2 }. {3}) ", ofield. getnameref (), ofield. getfieldtypename (ofield. getfieldtype (), ofield. getwidth (), ofield. getprecision ();} // number of elements in the output layer console. writeline ("number of elements = {0}", olayer. getfeaturecount (0); feature ofeature = NULL; // the elements in the layer are traversed below while (Ofeature = olayer. getnextfeature ())! = NULL) {console. writeline ("currently processed {0}: \ n property value:", ofeature. getfid (); // get the Attribute Table content in the element for (INT ifield = 0; ifield <ifieldcount; ifield ++) {fielddefn ofielddefn = odefn. getfielddefn (ifield); fieldtype = ofielddefn. getfieldtype (); Switch (type) {casefieldtype. oftstring: console. writeline ("{0} \ t", ofeature. getfieldasstring (ifield); break; casefieldtype. oftreal: console. writeline ("{0} \ t", ofeature. get Fieldasdouble (ifield); break; casefieldtype. oftinteger: console. writeline ("{0} \ t", ofeature. getfieldasinteger (ifield); break; default: console. writeline ("{0} \ t", ofeature. getfieldasstring (ifield); break ;}// obtain the ry ogeometry = ofeature in the element. getgeometryref (); // for demonstration, only one element Information break is output;} console. writeline ("disabled dataset! ");}

Tu Figure 1 OGR library use C # Read vector Example 1

Figure 2 example of using C # to read a vector in the OGR library 2

2. Write Vector

When using C # To create a vector image, use a string in WKT format to create it. You can also create an instance in other ways. The Code is as follows. The written vector graphics and Attribute Table 3 are shown.

Static void writevectorfile () {// to support Chinese paths, add the following code osgeo. gdal. gdal. setconfigoption ("gdal_filename_is_utf8", "no"); // to make the Attribute Table field support Chinese characters, add the following osgeo statement. gdal. gdal. setconfigoption ("shape_encoding", ""); string strvectorfile = "E: \ datum \ gdalcstest \ debug \ testpolygon. SHP "; // register all drivers. registerall (); // create data. Here we use the SHP File Created for ESRI as an example string strdrivername = "esrishapefile"; driver odriver = OGR. getdriverbyname (strdr Ivername); If (odriver = NULL) {console. writeline ("% s driver unavailable! \ N ", strvectorfile); return;} // create the data source datasource ODS = odriver. createdatasource (strvectorfile, null); If (ODS = NULL) {console. writeline ("failed to create Vector file [% s! \ N ", strvectorfile); return;} // creates a polygon layer. No space reference is specified here. If necessary, specify layer olayer = ODS here. createlayer ("testpolygon", null, wkbgeometrytype. wkbpolygon, null); If (olayer = NULL) {console. writeline ("layer creation failed! \ N "); return;} // create an Attribute Table below // first create an integer attribute fielddefn ofieldid = newfielddefn (" fieldid ", fieldtype. oftinteger); olayer. createfield (ofieldid, 1); // create another struct attribute named featurename with a length of 50 fielddefn ofieldname = newfielddefn ("fieldname", fieldtype. oftstring); ofieldname. setwidth (100); olayer. createfield (ofieldname, 1); featuredefn odefn = olayer. getlayerdefn (); // create a triangle element feature ofeaturetriangle = newf Eature (odefn); ofeaturetriangle. setfield (0, 0); ofeaturetriangle. setfield (1, "Triangle"); geometry geomtriangle = geometry. createfromwkt ("polygon (0)"); ofeaturetriangle. setgeometry (geomtriangle); olayer. createfeature (ofeaturetriangle); // create a rectangle element feature ofeaturerectangle = newfeature (odefn); ofeaturerectangle. setfield (0, 1); ofeaturerectangle. setfield (1, "rectangle"); geometry geomrectangle = Geometry. createfromwkt ("polygon (30, 60, 60, 30, 30, 30, 0)"); ofeaturerectangle. setgeometry (geomrectangle); olayer. createfeature (ofeaturerectangle); // create a pentagram element feature ofeaturepentagon = newfeature (odefn); ofeaturepentagon. setfield (0, 2); ofeaturepentagon. setfield (1, "pentagram"); geometry geompentagon = geometry. createfromwkt ("polygon (70 15,700,)"); ofeaturepentagon. setgeom Etry (geompentagon); olayer. createfeature (ofeaturepentagon); console. writeline ("\ n dataset created! \ N ");}

Figure 3 vector image written

3. Vector Data Management

Static void vectordelete (string strvectorfile) {// register all drivers OGR. registerall (); driver odriver = NULL; {// open the vector datasource ODS = OGR. open (strvectorfile, 0); If (ODS = NULL) {file. delete (strvectorfile); return;} odriver = ODS. getdriver (); If (odriver = NULL) {file. delete (strvectorfile); return ;}} if (odriver. deletedatasource (strvectorfile) = OGR. ogrerr_none) return; else file. delete (strvectorfile);} staticvoid vectorrename (string stroldfile, string strnewfile) {// register all drivers OGR. registerall (); driver odriver = NULL; {// open the vector datasource ODS = OGR. open (stroldfile, 0); If (ODS = NULL) {file. move (stroldfile, strnewfile); return;} odriver = ODS. getdriver (); If (odriver = NULL) {file. move (stroldfile, strnewfile); return;} datasource odds = odriver. copydatasource (ODS, strnewfile, null); If (odds = NULL) {file. move (stroldfile, strnewfile); Return ;}} if (odriver. deletedatasource (stroldfile) = OGR. ogrerr_none) return; else file. move (stroldfile, strnewfile );}