A generic procedure for Delphi (VCL or FMX). The driver is picked automatically from the path or URL, so it works with any registered format: SHP, TIFF, DXF, GeoPackage, WMS/WMTS URLs, .ttkls, and so on.

uses
  GisTypes, GisLayer, GisRegistredLayers,
  VCL.GisViewerWnd;   // or FMX.GisViewerWnd

function AddLayer( const _gis  : TGIS_ViewerWnd ;
                   const _path : String ;
                   const _name : String = '' ;
                   const _zoom : Boolean = True
                 ) : TGIS_Layer ;
begin
  Result := GisCreateLayer( _name, _path ) ;
  if not Assigned( Result ) then
    raise Exception.CreateFmt( 'Unsupported layer: %s', [ _path ] ) ;
  try
    Result.Open ;
    _gis.Add( Result ) ;
  except
    FreeAndNil( Result ) ;
    raise ;
  end ;

  if _zoom then
    _gis.FullExtent
  else
    _gis.InvalidateWholeMap ;
end ;

Usage:

AddLayer( GIS, 'C:\data\rivers.shp', 'rivers' ) ;
AddLayer( GIS, 'C:\data\ortho.tif' ) ;
if dlgOpen.Execute then AddLayer( GIS, dlgOpen.FileName ) ;

• GisCreateLayer returns nil when no registered driver recognizes the path.
• After a successful Add, the viewer owns the layer, so don't free it yourself. The except block frees it only when Open or Add fails.
• An empty _name makes the path become the layer name.
• To show a single file and replace everything in the viewer, GIS.Open( path ) is even simpler, but it closes the current project first.

Works in both WinForms and WPF because it takes the shared IGIS_Viewer interface. InvalidateWholeMap is confirmed in the .NET docs.

using System;
using TatukGIS.NDK;

public static class GisHelper
{
    public static TGIS_Layer AddLayer(
        IGIS_Viewer gis,
        string path,
        string name = "",
        bool zoom = true)
    {
        TGIS_Layer layer = TGIS_Utils.GisCreateLayer(name, path);
        if (layer == null)
            throw new NotSupportedException($"Unsupported layer: {path}");

        try
        {
            layer.Open();
            gis.Add(layer);
        }
        catch
        {
            layer.Dispose();
            throw;
        }

        if (zoom)
            gis.FullExtent();
        else
            gis.InvalidateWholeMap();

        return layer;
    }
}

Usage:

GisHelper.AddLayer(GIS, @"C:\data\rivers.shp", "rivers");
GisHelper.AddLayer(GIS, @"C:\data\ortho.tif");

var dlg = new OpenFileDialog();
if (dlg.ShowDialog() == DialogResult.OK)   // WPF: == true
    GisHelper.AddLayer(GIS, dlg.FileName);

• After a successful Add, the viewer owns the layer. The catch block disposes it only when Open or Add fails.
• An empty name gives the layer its default name.
• For a concrete viewer type, use TatukGIS.NDK.WinForms.TGIS_ViewerWnd or TatukGIS.NDK.WPF.TGIS_ViewerWnd.

SaveData saves only the data: shape geometry and attribute values. SaveAll saves the data plus the layer's settings (configuration and transformation). This holds on both the layer and the viewer.

Layer (TGIS_Layer)

Viewer (TGIS_ViewerWnd / IGIS_Viewer)

// after editing shapes: persist edits only
if (layer.MustSave())
    layer.SaveData();

// before closing: edits + styling/config
GIS.SaveAll();

// full session save: layers + project file
GIS.SaveAll();
GIS.SaveProject();

SaveProject() alone won't write your edits.