Fix smaller issues and add TODOs.

Author: lauxjpn

src/EFCore.Jet/Migrations/JetMigrationsSqlGenerator.cs

@@ -364,6 +364,12 @@ protected override void Generate(
             Check.NotNull(operation, nameof(operation));
             Check.NotNull(builder, nameof(builder));
 
+            // CHECK: Rename table operations require extensions like ADOX or DAO.
+            //       A native way to do this would be to:
+            //           1. CREATE TABLE `destination table`
+            //           2. INSERT INTO ... SELECT ... FROM
+            //           3. DROP TABLE `source table`
+            //           4. Recrete indices and references.
             builder.Append("RENAME TABLE ")
                 .Append(Dependencies.SqlGenerationHelper.DelimitIdentifier(operation.Name))
                 .Append(" TO ")

src/System.Data.Jet/AdoxWrapper.cs

@@ -24,6 +24,8 @@ public static void RenameTable(string connectionString, string tableName, string
             }
             catch (Exception e)
             {
+                // TODO: Try interating over the _Tables collection instead of using Item["TableName"].
+                
                 throw new Exception("Cannot rename table", e);
             }
             finally
@@ -48,7 +50,8 @@ public static void RenameColumn(string connectionString, string tableName, strin
             try
             {
                 using var tables = catalog.Tables;
-                using var columns = tables[tableName].Columns;
+                using var table = tables[tableName];
+                using var columns = table.Columns;
                 using var column = columns[columnName];
                 column.Name = newColumnName;
             }
@@ -92,8 +95,7 @@ public static string CreateEmptyDatabase(string fileNameOrConnectionString, DbPr
                 connection.DataAccessProviderFactory = dataAccessProviderFactory;
                 connection.Open();
 
-                string sql = @"
-CREATE TABLE `MSysAccessStorage` (
+                var sql = @"CREATE TABLE `MSysAccessStorage` (
     `DateCreate` DATETIME NULL,
     `DateUpdate` DATETIME NULL,
     `Id` COUNTER NOT NULL,
@@ -136,9 +138,9 @@ private static dynamic GetCatalogInstanceAndOpen(string errorPrefix, string conn
 
             try
             {
-                using dynamic cnn = new ComObject("ADODB.Connection");
-                cnn.Open(connectionString);
-                catalog.ActiveConnection = cnn;
+                using dynamic connection = new ComObject("ADODB.Connection");
+                connection.Open(connectionString);
+                catalog.ActiveConnection = connection;
             }
             catch (Exception e)
             {

src/System.Data.Jet/ComObject.cs

@@ -110,7 +110,7 @@ private static object WrapIfRequired(object obj)
 
         public void Dispose()
         {
-            // The RCW is a .NET object and cannot be released from the finalizer anymore,
+            // The RCW is a .NET object and cannot be released from the finalizer,
             // because it might not exist anymore.
             if (_instance != null)
             {

src/System.Data.Jet/JetConnection.cs

@@ -489,6 +489,9 @@ public static void ClearAllPools()
         public void CreateEmptyDatabase()
             => CreateEmptyDatabase(DataSource, DataAccessProviderFactory);
 
+        // TODO: Use the `CREATE_DB` connection string option instead of calling ADOX when using ODBC, to create
+        //       a new database file.
+        //       Alternatively, use DAO in conjunction with ODBC.
         public static string CreateEmptyDatabase(string fileNameOrConnectionString, DbProviderFactory dataAccessProviderFactory)
             => AdoxWrapper.CreateEmptyDatabase(fileNameOrConnectionString, dataAccessProviderFactory);
 

src/System.Data.Jet/JetStoreSchemaDefinition/JetRenameHandling.cs

@@ -22,7 +22,10 @@ public static bool TryDatabaseOperation(string connectionString, string commandT
             {
                 string tableName = match.Groups["tableName"].Value;
                 string newTableName = match.Groups["newTableName"].Value;
+                
+                // TODO: Only use ADOX in an OLE DB context. Use DAO in an ODBC context.
                 AdoxWrapper.RenameTable(connectionString, RemoveBrackets(tableName), RemoveBrackets(newTableName));
+                
                 return true;
             }