public string SpatialDataMember { get; set; }

Public Property SpatialDataMember As String

<Window
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:dxm="http://schemas.devexpress.com/winfx/2008/xaml/map"
        x:Class="SqlGeometryDataAdapterExample.MainWindow"
        Title="MainWindow" Height="350" Width="525">
    <Grid>
        <dxm:MapControl x:Name="mapControl">
            <dxm:MapControl.MapEditor>
                <dxm:MapEditor MapItemEdited="MapEditor_MapItemEdited"/>
            </dxm:MapControl.MapEditor>
            <dxm:VectorLayer DataLoaded="VectorLayer_DataLoaded">
                <dxm:VectorLayer.ShapeTitleOptions>
                    <dxm:ShapeTitleOptions Pattern="{}{TextCol}"
                                           Visible="True"/>
                </dxm:VectorLayer.ShapeTitleOptions>
                <dxm:SqlGeometryDataAdapter SqlText = "SELECT [id],[GeomCol1],[TextCol] FROM [dbo].[DemoTable]" 
                                            SpatialDataMember = "GeomCol1" ConnectionString="{Binding}"/>
            </dxm:VectorLayer>
        </dxm:MapControl>
    </Grid>
</Window>

using DevExpress.Xpf.Map;
using System;
using System.Data.SqlClient;
using System.IO;
using System.Windows;

namespace SqlGeometryDataAdapterExample {
    public partial class MainWindow : Window {

        const string filePath = "..\\..\\Data\\SQLG.mdf";
        static string fullFilePath = Path.GetFullPath(Path.Combine(AppDomain.CurrentDomain.BaseDirectory, filePath));
        public string ConnectionString { get; } = @"Data Source=(LocalDB)\MSSQLLocalDB;AttachDbFileName=" + fullFilePath + ";Database=SqlGeometryDB;Integrated Security=True;MultipleActiveResultSets=True";

        public MainWindow() {
            InitializeComponent();
            this.DataContext = ConnectionString;
        }

        private void MapEditor_MapItemEdited(object sender, DevExpress.Xpf.Map.MapItemEditedEventArgs e) {
            foreach (MapPath path in e.Items) {
                int id = Convert.ToInt32(path.Attributes["id"].Value);
                string modified = path.ExportToWkt().ToString();
                path.Attributes["TextCol"].Value = "Australia" + " " + DateTime.Now.Second.ToString();

                using (SqlConnection cn = new SqlConnection() { ConnectionString = this.ConnectionString }) {
                    cn.Open();
                    // For more information about SRID parameters, see https://docs.microsoft.com/en-us/sql/t-sql/spatial-geography/stsrid-geography-data-type?view=sql-server-ver15
                    SqlCommand updatecmd = new SqlCommand("UPDATE DemoTable SET GeomCol1 = geometry::STGeomFromText('" + modified + "', 4326 ) WHERE id = " + id.ToString(), cn);
                    updatecmd.ExecuteNonQuery();

                    SqlCommand updateattr = new SqlCommand("UPDATE DemoTable SET TextCol = '" + path.Attributes["TextCol"].Value.ToString() + "' WHERE id =" + id.ToString(), cn);
                    updateattr.ExecuteNonQuery();
                }
            }
        }

        private void VectorLayer_DataLoaded(object sender, DataLoadedEventArgs e) {
            mapControl.ZoomToFitLayerItems();
        }
    }
}

Imports DevExpress.Xpf.Map
Imports System
Imports System.Data.SqlClient
Imports System.IO
Imports System.Windows

Namespace SqlGeometryDataAdapterExample
    Partial Public Class MainWindow
        Inherits Window

        Private Const filePath As String = "..\..\Data\SQLG.mdf"
        Private Shared fullFilePath As String = Path.GetFullPath(Path.Combine(AppDomain.CurrentDomain.BaseDirectory, filePath))
        Public ReadOnly Property ConnectionString() As String = "Data Source=(LocalDB)\MSSQLLocalDB;AttachDbFileName=" & fullFilePath & ";Database=SqlGeometryDB;Integrated Security=True;MultipleActiveResultSets=True"

        Public Sub New()
            InitializeComponent()
            Me.DataContext = ConnectionString
        End Sub

        Private Sub MapEditor_MapItemEdited(ByVal sender As Object, ByVal e As DevExpress.Xpf.Map.MapItemEditedEventArgs)
            For Each path As MapPath In e.Items
                Dim id As Integer = Convert.ToInt32(path.Attributes("id").Value)
                Dim modified As String = path.ExportToWkt().ToString()
                path.Attributes("TextCol").Value = "Australia" & " " & DateTime.Now.Second.ToString()

                Using cn As New SqlConnection() With {.ConnectionString = Me.ConnectionString}
                    cn.Open()
                    ' For more information about SRID parameters, see https://docs.microsoft.com/en-us/sql/t-sql/spatial-geography/stsrid-geography-data-type?view=sql-server-ver15
                    Dim updatecmd As New SqlCommand("UPDATE DemoTable SET GeomCol1 = geometry::STGeomFromText('" & modified & "', 4326 ) WHERE id = " & id.ToString(), cn)
                    updatecmd.ExecuteNonQuery()

                    Dim updateattr As New SqlCommand("UPDATE DemoTable SET TextCol = '" & path.Attributes("TextCol").Value.ToString() & "' WHERE id =" & id.ToString(), cn)
                    updateattr.ExecuteNonQuery()
                End Using
            Next path
        End Sub

        Private Sub VectorLayer_DataLoaded(ByVal sender As Object, ByVal e As DataLoadedEventArgs)
            mapControl.ZoomToFitLayerItems()
        End Sub
    End Class
End Namespace