السمات والميزات - مكتبة C# GIS

الحصول على عدد الميزات في الطبقة

// For complete examples and data files, please go to https://github.com/aspose-gis/Aspose.GIS-for-.NET
using (VectorLayer layer = VectorLayer.Open(dataDir + "InputShapeFile.shp", Drivers.Shapefile))
{
    Console.WriteLine("Total Features in this file: " + layer.Count);
}

الحصول على معلومات حول سمات الطبقة

// For complete examples and data files, please go to https://github.com/aspose-gis/Aspose.GIS-for-.NET
using (VectorLayer layer = VectorLayer.Open(dataDir + "InputShapeFile.shp", Drivers.Shapefile))
{
    Console.WriteLine("The layer has {0} attributes defined.\n", layer.Attributes.Count);
    foreach (FeatureAttribute attribute in layer.Attributes)
    {
        Console.WriteLine("Name: {0}", attribute.Name);
        Console.WriteLine("Data type: {0}", attribute.DataType);
        Console.WriteLine("Can be null: {0}", attribute.CanBeNull);
    }
}

التكرار على الميزات في الطبقة

// For complete examples and data files, please go to https://github.com/aspose-gis/Aspose.GIS-for-.NET
using (VectorLayer layer = VectorLayer.Open(dataDir + "InputShapeFile.shp", Drivers.Shapefile))
{
    foreach (Feature feature in layer)
    {
        Console.WriteLine(feature.Geometry.AsText());
    }
}

الحصول على قيمة سمة ميزة

// For complete examples and data files, please go to https://github.com/aspose-gis/Aspose.GIS-for-.NET
using (VectorLayer layer = VectorLayer.Open(dataDir + "InputShapeFile.shp", Drivers.Shapefile))
{
    for (int i = 0; i < layer.Count; i++)
    {
        Feature feature = layer[i];
        Console.WriteLine("Entry {0} information\n ========================", i);

        // case 1
        string nameValue = feature.GetValue<string>("name"); // attribute name is case-sensitive
        int ageValue = feature.GetValue<int>("age");
        string dobValue = feature.GetValue<DateTime>("dob").ToString();
        Console.WriteLine("Attribute value for feature #{0} is: {1}, {2}", nameValue, ageValue, dobValue);

        // case 2
        var objName = feature.GetValue("name"); // attribute name is case-sensitive
        var objAge = feature.GetValue("age");
        var objDob = feature.GetValue("dob");
        Console.WriteLine("Attribute object for feature #{0} is: {1}, {2}", objName, objAge, objDob);
    }
}

الحصول على قيم سمة ميزة

// For complete examples and data files, please go to https://github.com/aspose-gis/Aspose.GIS-for-.NET
using (VectorLayer layer = VectorLayer.Open(dataDir + "InputShapeFile.shp", Drivers.Shapefile))
{
    foreach (var feature in layer)
    {
        // reads all the attributes into an array.
        object[] all = new object[3];
        feature.GetValues(all);
        Console.WriteLine("all    : {0}, {1}, {2}", all);

        // reads several the attributes into an array.
        object[] several = new object[2];
        feature.GetValues(several);
        Console.WriteLine("several: {0}, {1}", several);

        // reads the attributes as dump of objects.
        var dump = feature.GetValuesDump();
        Console.WriteLine("dump   : {0}, {1}, {2}", dump);

        Console.WriteLine();
    }
}

تصفية الميزات حسب قيمة السمة

// For complete examples and data files, please go to https://github.com/aspose-gis/Aspose.GIS-for-.NET
using (VectorLayer layer = VectorLayer.Open(dataDir + "InputShapeFile.shp", Drivers.Shapefile))
{
    // all features with the date value in the attribute "dob" later than 1982-01-01.
    foreach (Feature feature in layer.WhereGreater("dob", new DateTime(1982, 1, 1, 0, 0, 0)))
    {
        Console.WriteLine(feature.GetValue<DateTime>("dob").ToShortDateString());
    }
}

استخراج الميزات من ملف ShapeFile إلى GeoJSON

// For complete examples and data files, please go to https://github.com/aspose-gis/Aspose.GIS-for-.NET
using (VectorLayer inputLayer = VectorLayer.Open(dataDir + "InputShapeFile.shp", Drivers.Shapefile))
{
    using (VectorLayer outputLayer = VectorLayer.Create(dataDir + "ExtractFeaturesFromShapeFileToGeoJSON_out.json", Drivers.GeoJson))
    {
        outputLayer.CopyAttributes(inputLayer);
        foreach (Feature inputFeature in inputLayer)
        {
            DateTime? date = inputFeature.GetValue<DateTime?>("dob");
            if (date == null || date < new DateTime(1982, 1, 1))
            {
                continue;
            }

            //Construct a new feature
            Feature outputFeature = outputLayer.ConstructFeature();
            outputFeature.Geometry = inputFeature.Geometry;
            outputFeature.CopyValues(inputFeature);
            outputLayer.Add(outputFeature);
        }
    }
}

تحديد طول قيمة السمة

// For complete examples and data files, please go to https://github.com/aspose-gis/Aspose.GIS-for-.NET
using (VectorLayer layer = VectorLayer.Create(dataDir + "SpecifyAttributeValueLength_out.shp", Drivers.Shapefile))
{
    // add attributes before adding features
    FeatureAttribute attribute = new FeatureAttribute("wide", AttributeDataType.String);
    attribute.Width = 120;
    layer.Attributes.Add(attribute);

    Feature feature = layer.ConstructFeature();
    feature.SetValue("wide", "this string can be up to 120 characters long now.");
    layer.Add(feature);
}

الحصول على قيمة سمة فارغة

// For complete examples and data files, please go to https://github.com/aspose-gis/Aspose.GIS-for-.NET
using (VectorLayer layer = VectorLayer.Open(dataDir + "InputShapeFile.shp", Drivers.Shapefile))
{
    int index = 0;
    foreach (Feature feature in layer)
    {
        DateTime? date = feature.GetValue<DateTime?>("dob");
        Console.WriteLine("Feature #{0}", index);
        Console.WriteLine("\tAttribute value present: {0}", date.HasValue);
        if (date.HasValue)
        {
            Console.WriteLine("\tAttribute value: {0}", date.Value);
        }
        index++;
    }
}

الحصول على قيمة أو القيمة الافتراضية للميزة

// For complete examples and data files, please go to https://github.com/aspose-gis/Aspose.GIS-for-.NET
//You can set default value for a feature of attribute in a layer
using (var layer = Drivers.GeoJson.CreateLayer(dataDir + "data1_out.json"))
{
    var attribute = new FeatureAttribute("attribute", AttributeDataType.Integer);
    attribute.CanBeNull = true;
    attribute.CanBeUnset = true;

    layer.Attributes.Add(attribute);

    Feature feature = layer.ConstructFeature();
    int? nullValue = feature.GetValueOrDefault<int?>("attribute"); // value == null
    var defValue1 = feature.GetValueOrDefault<int?>("attribute", 10); // value == 10
    var defValue2 = feature.GetValueOrDefault("attribute", 25); // value == 10
    Console.WriteLine($"'{nullValue}' vs '{defValue1}' vs '{defValue2}'");
}

//Another example where we set the default value to 100
using (var layer = Drivers.GeoJson.CreateLayer(dataDir + "data2_out.json"))
{
    var attribute = new FeatureAttribute("attribute", AttributeDataType.Double);
    attribute.CanBeNull = false;
    attribute.CanBeUnset = false;
    attribute.DefaultValue = 100;

    layer.Attributes.Add(attribute);

    Feature feature = layer.ConstructFeature();
    double defValue1 = feature.GetValueOrDefault<double>("attribute"); // value == 100
    var defValue2 = feature.GetValueOrDefault("attribute"); // value == 100
    feature.SetValue("attribute", 50);
    var newValue = feature.GetValueOrDefault<double>("attribute"); // value == 50
    Console.WriteLine($"'{defValue1}' vs '{defValue2}' vs '{newValue}'");
}