SqlServer: Add check for Transaction being zombied

Author: alex-kulakov

Orm/Xtensive.Orm.SqlServer/Sql.Drivers.SqlServer/Connection.cs

@@ -97,6 +97,74 @@ public override void BeginTransaction(IsolationLevel isolationLevel)
       activeTransaction = underlyingConnection.BeginTransaction(isolationLevel);
     }
 
+    /// <inheritdoc/>
+    public override void Commit()
+    {
+      EnsureIsNotDisposed();
+      EnsureTransactionIsActive();
+
+      try {
+        if (!IsTransactionZombied()) {
+          ActiveTransaction.Commit();
+        }
+      }
+      finally {
+        ActiveTransaction.Dispose();
+        ClearActiveTransaction();
+      }
+    }
+
+    /// <inheritdoc/>
+    public override async Task CommitAsync(CancellationToken token = default)
+    {
+      EnsureIsNotDisposed();
+      EnsureTransactionIsActive();
+
+      try {
+        if (!IsTransactionZombied()) {
+          await ActiveTransaction.CommitAsync(token).ConfigureAwait(false);
+        }
+      }
+      finally {
+        await ActiveTransaction.DisposeAsync().ConfigureAwait(false);
+        ClearActiveTransaction();
+      }
+    }
+
+    /// <inheritdoc/>
+    public override void Rollback()
+    {
+      EnsureIsNotDisposed();
+      EnsureTransactionIsActive();
+
+      try {
+        if (!IsTransactionZombied()) {
+          ActiveTransaction.Rollback();
+        }
+      }
+      finally {
+        ActiveTransaction.Dispose();
+        ClearActiveTransaction();
+      }
+    }
+
+    /// <inheritdoc/>
+    public override async Task RollbackAsync(CancellationToken token = default)
+    {
+      EnsureIsNotDisposed();
+      EnsureTransactionIsActive();
+
+      try {
+        if (!IsTransactionZombied()) {
+          await ActiveTransaction.RollbackAsync(token).ConfigureAwait(false);
+        }
+      }
+      finally {
+        await ActiveTransaction.DisposeAsync().ConfigureAwait(false);
+        ClearActiveTransaction();
+      }
+    }
+
     /// <inheritdoc/>
     public override void MakeSavepoint(string name)
     {
@@ -200,6 +268,11 @@ private async Task OpenWithCheckAsync(string checkQueryString, CancellationToken
       }
     }
 
+    private bool IsTransactionZombied()
+    {
+      return ActiveTransaction != null && ActiveTransaction.Connection == null;
+    }
+
     // Constructors
 
     public Connection(SqlDriver driver, bool checkConnection)