Dual table: Auto detect the dual table name on model load. Use that table for any queries.

Also allow a custom override name to be set

Author: ChrisJollyAU

src/EFCore.Jet.Data/JetConfiguration.cs

@@ -33,8 +33,8 @@ public static object IntegerNullValue
             }
         }
 
-        public static DataAccessProviderType DefaultDataAccessProviderType { get; set; } = DataAccessProviderType.Odbc; 
-        
+        public static DataAccessProviderType DefaultDataAccessProviderType { get; set; } = DataAccessProviderType.Odbc;
+
         // The SQL statement
         //
         // (SELECT COUNT(*) FROM MSysRelationships)
@@ -57,17 +57,13 @@ public static object IntegerNullValue
         /// <summary>
         /// The DUAL table or query
         /// </summary>
-        public static string DUAL { get; set; } = DUALForAccdb;
+        public static string CustomDualTableName = "";
+        //MSysRelationships
+        //MSysAccessStorage
+        //#Dual
+        //(SELECT COUNT(*) FROM MSysAccessStorage)
 
-        /// <summary>
-        /// The dual table for accdb
-        /// </summary>
-        public const string DUALForMdb = "(SELECT COUNT(*) FROM MSysRelationships)";
-
-        /// <summary>
-        /// The dual table for accdb
-        /// </summary>
-        public const string DUALForAccdb = "(SELECT COUNT(*) FROM MSysAccessStorage)";
+        public static string DetectedDualTableName = "#Dual";
 
         /// <summary>
         /// Gets or sets a value indicating whether show SQL statements.

src/EFCore.Jet/Query/Sql/Internal/JetQuerySqlGenerator.cs

@@ -224,7 +224,7 @@ private bool IsNonComposedSetOperation(SelectExpression selectExpression)
         protected override void GeneratePseudoFromClause()
         {
             Sql.AppendLine()
-                .Append("FROM " + JetConfiguration.DUAL);
+                .Append("FROM " + "(SELECT COUNT(*) FROM `" + (string.IsNullOrEmpty(JetConfiguration.CustomDualTableName) ? JetConfiguration.DetectedDualTableName : JetConfiguration.CustomDualTableName) + "`)");
         }
 
         private void GenerateList<T>(

src/EFCore.Jet/Scaffolding/Internal/JetDatabaseModelFactory.cs

@@ -105,7 +105,21 @@ public override DatabaseModel Create(
                     table.Database = databaseModel;
                     databaseModel.Tables.Add(table);
                 }
-                
+
+                var tableNames = databaseModel.Tables.Select(t => t.Name).ToList();
+                if (tableNames.Contains("MSysAccessStorage"))
+                {
+                    JetConfiguration.DetectedDualTableName = "MSysAccessStorage";
+                }
+                else if (tableNames.Contains("MSysRelationships"))
+                {
+                    JetConfiguration.DetectedDualTableName = "MSysRelationships";
+                }
+                else if (tableNames.Contains("#Dual"))
+                {
+                    JetConfiguration.DetectedDualTableName = "#Dual";
+                }
+
                 return databaseModel;
             }
             finally