Added new kb article map-center-on-selected-marker (#2583)

* Added new kb article map-center-on-selected-marker

* kb(Map): address comments

---------

Co-authored-by: KB Bot <[email protected]>
Co-authored-by: Hristian Stefanov <[email protected]>

Author: 3 people

knowledge-base/map-center-on-selected-marker.md

@@ -0,0 +1,107 @@
+---
+title: Center Map on Selected Marker
+description: Learn how to programmatically center a Telerik Map for Blazor component on a marker selected from a list.
+type: how-to
+page_title: How to Center a Map on Marker in Blazor Applications
+slug: map-kb-center-on-selected-marker
+tags: blazor, map, marker
+res_type: kb
+ticketid: 1671734
+---
+
+## Environment
+
+<table>
+    <tbody>
+	    <tr>
+	    	<td>Product</td>
+	    	<td>Map for Blazor</td>
+	    </tr>
+    </tbody>
+</table>
+
+## Description
+
+There's a list of markers. I need to center the map on a marker when it's selected from the list. 
+
+How can I dynamically update the center of a map based on a marker's coordinates?
+
+## Solution
+
+To center the map on a specific marker's coordinates, use a variable to bind the `Center` parameter of the `TelerikMap` component. Update this variable whenever a selection is made from the list. Here's how you can implement this:
+
+1. Use a component like the `TelerikDropDownList` to display the list of markers. Handle the `OnChange` event to update the map's center.
+
+2. In the `OnChange` event handler, update the map's `Center` property value to the coordinates of the selected marker.
+
+>caption Centering the Map on a Selected Marker
+
+````RAZOR
+<TelerikDropDownList Data="@MarkerData"
+                     @bind-Value="@SelectedValue"
+                     TextField="@nameof(MarkerModel.Title)"
+                     ValueField="@nameof(MarkerModel.Id)"
+                     OnChange="@MyOnChangeHandler">
+</TelerikDropDownList>
+
+<TelerikMap Center="@MapCenter"
+            Zoom="@MapZoom">
+    <MapLayers>
+        <MapLayer Type="@MapLayersType.Tile"
+                  Attribution="@LayerAttribution"
+                  Subdomains="@LayerSubdomains"
+                  UrlTemplate="@LayerUrlTemplate">
+        </MapLayer>
+
+        <MapLayer Type="@MapLayersType.Marker"
+                  Data="@MarkerData"
+                  LocationField="@nameof(MarkerModel.LatLng)"
+                  TitleField="@nameof(MarkerModel.Title)">
+        </MapLayer>
+    </MapLayers>
+</TelerikMap>
+
+@code {
+    private double[] MapCenter { get; set; } = new double[] { 30.268107, -97.744821 };
+    private int SelectedValue { get; set; }
+    private int MapZoom { get; set; } = 3;
+
+    private readonly string[] LayerSubdomains = new string[] { "a", "b", "c" };
+    private const string LayerUrlTemplate = "https://#= subdomain #.tile.openstreetmap.org/#= zoom #/#= x #/#= y #.png";
+    private const string LayerAttribution = "&copy; <a href='https://osm.org/copyright'>OpenStreetMap contributors</a>";
+
+    private void MyOnChangeHandler(object theUserInput)
+    {
+        int selectedId = (int)theUserInput;
+        MapCenter = MarkerData.First(i => i.Id == selectedId).LatLng;
+    }
+
+    private List<MarkerModel> MarkerData { get; set; } = new List<MarkerModel>() {
+        new MarkerModel()
+        {
+            Id = 0,
+            LatLng = new double[] { 30.268107, -97.744821 },
+            Title = "Austin, TX"
+        },
+        new MarkerModel()
+        {
+            Id = 1,
+            LatLng = new double[] { 37.7749, -122.4194 },
+            Title = "San Francisco, CA"
+        }
+    };
+
+    public class MarkerModel
+    {
+        public int Id { get; set; }
+        public double[]? LatLng { get; set; }
+        public string Title { get; set; } = string.Empty;
+    }
+}
+```
+
+## See Also
+
+- [Map Overview](https://docs.telerik.com/blazor-ui/components/map/overview)
+- [Map Markers](https://docs.telerik.com/blazor-ui/components/map/layers/marker)
+- [DropDownList Overview](https://docs.telerik.com/blazor-ui/components/dropdownlist/overview)