small fixes in excel manager

Author: morrisjdev

src/Example/Data/Context.cs

@@ -23,7 +23,7 @@ public class Context : DbContext
         protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
         {
             //Default: JSON-Serialize
-            optionsBuilder.UseFileContext();
+            //optionsBuilder.UseFileContext();
 
             //JSON-Serialize + simple Encryption
             //optionsBuilder.UseFileContext(new FileContextCore.Serializer.JSONSerializer(), new FileContextCore.FileManager.EncryptedFileManager());
@@ -35,7 +35,7 @@ protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
             //optionsBuilder.UseFileContext(new FileContextCore.Serializer.CSVSerializer());
 
             //Excel
-            //optionsBuilder.UseFileContext(new FileContextCore.CombinedManager.ExcelManager());
+            optionsBuilder.UseFileContext(new FileContextCore.CombinedManager.ExcelManager());
         }
 
         protected override void OnModelCreating(ModelBuilder modelBuilder)

src/Example/Data/Entities/User.cs

@@ -14,6 +14,8 @@ public class User : Base
 
         public string Name { get; set; }
 
+        public int? test { get; set; }
+
         public virtual List<Content> Contents { get; set; }
 
         public virtual List<Setting> Settings { get; set; }

src/Example/Program.cs

@@ -36,7 +36,7 @@ public static void Main(string[] args)
             User us = new User()
             {
                 Name = "Morris Janatzek",
-                Username = "astalawixer"
+                Username = null
             };
 
             db.Users.Add(us);

src/FileContextCore/CombinedManager/ExcelManager.cs

@@ -87,7 +87,8 @@ public List<T> GetItems<T>()
                         }
                         else
                         {
-                            prop.Value.SetValue(item, Convert.ChangeType(ws.Cells[i + 1, prop.Key].Value, type));
+                            object value = ws.Cells[i + 1, prop.Key].Value;
+                            prop.Value.SetValue(item, value != null ? Convert.ChangeType(value, type) : value);
                         }
                     }
 
@@ -154,7 +155,7 @@ public void SaveItems<T>(List<T> list)
                 {
                     PropertyInfo pi = props[x];
 
-                    ws.SetValue(i + 2, x + 1, pi.GetValue(item).ToString());
+                    ws.SetValue(i + 2, x + 1, pi.GetValue(item)?.ToString());
                 }
             }