在要素集点空间中设置字段值

Question

我正在使用 Microsoft Visual Studio 和 C# 编程语言中的 DotSpatial 库创建一个 shapefile。 shapefile 由多边形层组成。图层中的每个多边形都需要具有特定的肥料值。据我的理解，我必须首先创建一个字段（例如“肥料值”），然后为创建的每个多边形添加相应的肥料值。我创建了一个字段并创建了一个多边形。但是，我仍在努力寻找在相应的多边形中添加字段值的正确方法。代码如下：

// Create a feature set of type Polygon and set the projection
FeatureSet fs = new FeatureSet(FeatureType.Polygon);
fs.Projection = ProjectionInfo.FromAuthorityCode("EPSG", 3857);

// Get the DataTable and set the fertilizer field
DataTable table = fs.DataTable;
DataColumn FertilizerField = table.Columns.Add("Fertilizer Value", typeof(double));

// Adding a Polygon feature to the layer 
Coordinate[] coord = new Coordinate[]
{
    new Coordinate(0.0, 0.0),
    new Coordinate(1.0, 0.0),
    new Coordinate(1.0, 1.0),
    new Coordinate(0.0, 1.0),
    new Coordinate(0.0, 0.0)
};
fs.AddFeature(new Polygon(new LinearRing(coord)));

// TODO: HOW TO ADD FERTILIZER VALUE OF 100 TO THE FERTILIZER FIELD OF THIS POLYGON?

我的问题是，如何设置该多边形的字段值？

Answer 1

您可以创建一个Feature变量，然后更新DataRow属性上的内容。然后，您必须直接将该功能添加到 Features 集合中，而不是使用 AddFeature 快捷方法。

        // Create a feature set of type Polygon and set the projection
        FeatureSet fs = new FeatureSet(FeatureType.Polygon);
        fs.Projection = ProjectionInfo.FromAuthorityCode("EPSG", 3857);

        // Get the DataTable and set the fertilizer field
        DataTable table = fs.DataTable;
        DataColumn FertilizerField = table.Columns.Add("Fertilizer Value", typeof(double));

        // Adding a Polygon feature to the layer 
        Coordinate[] coord = new Coordinate[]
        {
            new Coordinate(0.0, 0.0),
            new Coordinate(1.0, 0.0),
            new Coordinate(1.0, 1.0),
            new Coordinate(0.0, 1.0),
            new Coordinate(0.0, 0.0)
        };
        // Create a Feature Variable to update the shape with attribute content.
        Feature f = new Feature(new Polygon(new LinearRing(coord)));
        // Modify the data row like any DataTable DataRow object.
        f.DataRow["Fertilizer Value"] = 100;
        // Add the fully created feature to the list of features directly.
        fs.Features.Add(f);

Answer 2

由于

fs.AddFeature(new Polygon(new LinearRing(coord)));

将创建的要素作为 IFeature 对象返回，您可以将此对象分配给变量，然后使用其 DataRow 属性来分配您的“肥料值”

代码应如下所示：

        // Create a feature set of type Polygon and set the projection
        FeatureSet fs = new FeatureSet(FeatureType.Polygon);
        fs.Projection = ProjectionInfo.FromAuthorityCode("EPSG", 3857);

        // Get the DataTable and set the fertilizer field
        DataTable table = fs.DataTable;
        DataColumn FertilizerField = table.Columns.Add("Fertilizer Value", typeof(double));

        // Adding a Polygon feature to the layer 
        Coordinate[] coord = new Coordinate[]
        {
            new Coordinate(0.0, 0.0),
            new Coordinate(1.0, 0.0),
            new Coordinate(1.0, 1.0),
            new Coordinate(0.0, 1.0),
            new Coordinate(0.0, 0.0)
        };
        // Create a Feature Variable to update the shape with attribute content.
        IFeature f = fs.AddFeature(new Polygon(new LinearRing(coord)));
        // Modify the data row like any DataTable DataRow object.
        f.DataRow["Fertilizer Value"] = 100;