Managing View Extent

There are many ways to set and retrieve the extent of a view in GeoBlazor.

Setting the extent in Razor Component Markup

The advantage of setting the extent in Razor markup is that it will be read before the view is rendered.

1. You can set the Extent property directly inside the MapView. The SpatialReference is required when defining the Extent in markup.

<MapView>
    <Extent XMin="-14092388.508390034"
            XMax="-8427487.468120558"
            YMin="2705131.7741284175"
            YMax="6452380.648779902">
        <SpatialReference Wkid="102100" />
    </Extent>
    <Map ArcGisDefaultBasemap="arcgis-topographic" />
</MapView>

1. You can also set the Center (Long/Lat) and Zoom or Scale parameters on MapView to define an extent.

<MapView Longitude="-118.80500" Latitude="34.02700" Zoom="13">
    <Map ArcGisDefaultBasemap="arcgis-topographic" />
</MapView>

Setting either Extent’s or MapView’s parameters to a variable would allow one to alter the extent programmatically after rendering. However, it should be noted that if a user interacts with the view manually via drag, pinch-to-zoom, or the zoom controls, or any of the MapView.Set methods listed below are called, the Razor component parameters will be disabled from controlling the extent until the view is re-rendered, such as by calling mapView.Refresh().

Setting the extent in C# code

Once the view is rendered, it may be necessary to change the view’s extent in code.

1. SetExtent allows you to directly alter the current view extent.

await mapView.SetExtent(new Extent
{
    XMin = -14092388.508390034,
    XMax = -8427487.468120558,
    YMin = 2705131.7741284175,
    YMax = 6452380.648779902,
    SpatialReference = new SpatialReference { Wkid = 102100 }
});

1. GoTo(extent) is similar to SetExtent, but it provides more animation.

await mapView.GoTo(new Extent
{
    XMin = -14092388.508390034,
    XMax = -8427487.468120558,
    YMin = 2705131.7741284175,
    YMax = 6452380.648779902,
    SpatialReference = new SpatialReference { Wkid = 102100 }
});

1. SetCenter and SetZoom allow you to set the center and zoom level of the view.

await mapView.SetCenter(new MapPoint(-118.80500, 34.02700));
await mapView.SetZoom(13);

As mentioned above, once these methods are called, the Razor component markup parameters will be ignore on further page renders, until mapView.Refresh() is called or the entire view is re-loaded.