Add missing information about accessing DB (#2423)

Author: tvedeane

exercises/concept/object-relational-mapping/.docs/instructions.md

@@ -15,6 +15,15 @@ The database has the following instance methods:
 - `Database.EndTransaction()` commits the transaction to the database. It may throw an exception if it can't close the transaction or if `Database.BeginTransaction()` had not been called.
 - A call to`Database.Dispose()` will clean up the database if an exception is thrown during a transaction. This will change the state of the database to `Closed`.
 
+The state of the database can be accessed using `database.DbState`.
+
+The state of the database can be set to one of:
+
+- TransactionStarted
+- DataWritten
+- Invalid
+- Closed
+
 ## 1. Begin a transaction
 
 Implement `Orm.Begin()` to start a transaction on the database. If the database does not start with an internal state of `State.Closed` then it throws an `InvalidOperationException`.

exercises/concept/object-relational-mapping/.meta/config.json

@@ -13,6 +13,9 @@
     "test": [
       "ObjectRelationalMappingTests.cs"
     ],
+  "invalidator": [
+      "Database.cs"
+    ],
     "exemplar": [
       ".meta/Exemplar.cs"
     ],

exercises/concept/object-relational-mapping/Database.cs

@@ -0,0 +1,54 @@
+public class Database : IDisposable
+{
+    public enum State { TransactionStarted, DataWritten, Invalid, Closed }
+
+    public State DbState { get; private set; } = State.Closed;
+    public string lastData = string.Empty;
+
+    public void BeginTransaction()
+    {
+        if (DbState != State.Closed)
+        {
+            throw new InvalidOperationException();
+        }
+        DbState = State.TransactionStarted;
+    }
+
+    public void Write(string data)
+    {
+        if (DbState != State.TransactionStarted)
+        {
+            throw new InvalidOperationException();
+        }
+        // this does something significant with the db transaction object
+        lastData = data;
+        if (data == "bad write")
+        {
+            DbState = State.Invalid;
+            throw new InvalidOperationException();
+        }
+
+        DbState = State.DataWritten;
+    }
+
+    public void EndTransaction()
+    {
+        if (DbState != State.DataWritten && DbState != State.TransactionStarted)
+        {
+            throw new InvalidOperationException();
+        }
+        // this does something significant to end the db transaction object
+        if (lastData == "bad commit")
+        {
+            DbState = State.Invalid;
+            throw new InvalidOperationException();
+        }
+
+        DbState = State.Closed;
+    }
+
+    public void Dispose()
+    {
+        DbState = State.Closed;
+    }
+}

exercises/concept/object-relational-mapping/ObjectRelationalMappingTests.cs

@@ -79,58 +79,3 @@ public void Disposable()
     }
 }
 
-// **** please do not modify the Database class ****
-public class Database : IDisposable
-{
-    public enum State { TransactionStarted, DataWritten, Invalid, Closed }
-
-    public State DbState { get; private set; } = State.Closed;
-    public string lastData = string.Empty;
-
-    public void BeginTransaction()
-    {
-        if (DbState != State.Closed)
-        {
-            throw new InvalidOperationException();
-        }
-        DbState = State.TransactionStarted;
-    }
-
-    public void Write(string data)
-    {
-        if (DbState != State.TransactionStarted)
-        {
-            throw new InvalidOperationException();
-        }
-        // this does something significant with the db transaction object
-        lastData = data;
-        if (data == "bad write")
-        {
-            DbState = State.Invalid;
-            throw new InvalidOperationException();
-        }
-
-        DbState = State.DataWritten;
-    }
-
-    public void EndTransaction()
-    {
-        if (DbState != State.DataWritten && DbState != State.TransactionStarted)
-        {
-            throw new InvalidOperationException();
-        }
-        // this does something significant to end the db transaction object
-        if (lastData == "bad commit")
-        {
-            DbState = State.Invalid;
-            throw new InvalidOperationException();
-        }
-
-        DbState = State.Closed;
-    }
-
-    public void Dispose()
-    {
-        DbState = State.Closed;
-    }
-}