Merge pull request #2591 from PrismLibrary/issue-2570

Added CanShowDialog method to IPageDialogService

src/Forms/Prism.Forms/Common/ApplicationProvider.cs

@@ -10,7 +10,7 @@ public class ApplicationProvider : IApplicationProvider
         /// <inheritdoc/>
         public Page MainPage
         {
-            get { return Application.Current.MainPage; }
+            get { return Application.Current?.MainPage; }
             set { Application.Current.MainPage = value; }
         }
     }

src/Forms/Prism.Forms/Services/PageDialogService/IPageDialogService.cs

@@ -8,6 +8,12 @@ namespace Prism.Services
     /// </summary>
     public interface IPageDialogService
     {
+        /// <summary>
+        /// Determines if the dialog can be shown.
+        /// </summary>
+        /// <returns>True if you can show the dialog; False if the dialog cannot be shown</returns>
+        bool CanShowDialog();
+
         /// <summary>
         /// Presents an alert dialog to the application user with an accept and a cancel button.
         /// </summary>

src/Forms/Prism.Forms/Services/PageDialogService/PageDialogService.cs

@@ -185,5 +185,14 @@ public virtual Task<string> DisplayPromptAsync(string title, string message, str
             var keyboard = _keyboardMapper.Map(keyboardType);
             return _applicationProvider.MainPage.DisplayPromptAsync(title, message, accept, cancel, placeholder, maxLength, keyboard, initialValue);
         }
+
+        /// <summary>
+        /// Determines if the dialog can be shown.
+        /// </summary>
+        /// <returns>True if you can show the dialog; False if the dialog cannot be shown</returns>
+        public bool CanShowDialog()
+        {
+            return _applicationProvider.MainPage != null;
+        }
     }
 }