Modify DatabaseObject to support state

This makes DatabaseUser simpler to work with. It can store a reference to the database the user should be created in, and the class can handle switching to/from that database.

Author: edwardneal

src/Microsoft.Data.SqlClient/tests/Common/Fixtures/DatabaseObjects/DatabaseObject.cs

@@ -12,21 +12,28 @@ namespace Microsoft.Data.SqlClient.Tests.Common.Fixtures.DatabaseObjects;
 /// Base class for a transient database object (such as a table, type or
 /// stored procedure.)
 /// </summary>
-public abstract class DatabaseObject : IDisposable
+/// <typeparam name="TState">
+/// The type of the internal state accessible to derived types at the point of object creation
+/// via the <see cref="State"/> property.
+/// </typeparam>
+public abstract class DatabaseObject<TState> : IDisposable
 {
     private readonly bool _shouldDrop;
 
     protected SqlConnection Connection { get; }
 
+    protected TState State { get; }
+
     public string Name { get; }
 
     public string UnescapedName => Name.Substring(1, Name.Length - 2).Replace("]]", "]");
 
-    protected DatabaseObject(SqlConnection connection, string name, string definition, bool shouldCreate, bool shouldDrop)
+    protected DatabaseObject(SqlConnection connection, string name, string definition, TState state, bool shouldCreate, bool shouldDrop)
     {
         _shouldDrop = shouldDrop;
 
         Connection = connection;
+        State = state;
         Name = name;
 
         if (shouldCreate)
@@ -263,3 +270,15 @@ public void Dispose()
         GC.SuppressFinalize(this);
     }
 }
+
+/// <summary>
+/// Base class for a transient database object (such as a table, type or
+/// stored procedure.)
+/// </summary>
+public abstract class DatabaseObject : DatabaseObject<object?>
+{
+    protected DatabaseObject(SqlConnection connection, string name, string definition, bool shouldCreate, bool shouldDrop)
+        : base(connection, name, definition, state: null, shouldCreate, shouldDrop)
+    {
+    }
+}

src/Microsoft.Data.SqlClient/tests/Common/Fixtures/DatabaseObjects/DatabaseUser.cs

@@ -10,48 +10,54 @@ namespace Microsoft.Data.SqlClient.Tests.Common.Fixtures.DatabaseObjects;
 /// <remarks>
 /// This class assumes that the associated server login already exists.
 /// </remarks>
-public sealed class DatabaseUser : DatabaseObject
+public sealed class DatabaseUser : DatabaseObject<string>
 {
-    private readonly string _databaseName;
+    public string DatabaseName => State;
 
     /// <summary>
     /// Initializes a new instance of the DatabaseUser class using the specified SQL connection
     /// and associated server login.
     /// </summary>
     /// <param name="connection">The SQL connection used to interact with the database.</param>
+    /// <param name="database">The name of the database where the user will be created.</param>
     /// <param name="login">The server login which the database user will be associated with.</param>
-    public DatabaseUser(SqlConnection connection, ServerLogin login)
-        : base(connection, login.Name, $"FOR LOGIN {login.Name}", shouldCreate: true, shouldDrop: true)
+    public DatabaseUser(SqlConnection connection, string database, ServerLogin login)
+        : base(connection, login.Name, $"FOR LOGIN {login.Name}", database, shouldCreate: true, shouldDrop: true)
     {
-        _databaseName = Connection.Database;
     }
 
     protected override void CreateObject(string definition)
     {
         using SqlCommand createCommand = new($"CREATE USER {Name} {definition}", Connection);
 
-        createCommand.ExecuteNonQuery();
+        ExecuteCommandInDatabase(createCommand);
     }
 
     protected override void DropObject()
     {
-        string? originalDatabase = _databaseName == Connection.Database ? null : _databaseName;
         using SqlCommand dropCommand = new($"IF USER_ID('{UnescapedName}') IS NOT NULL DROP USER {Name}", Connection);
 
+        ExecuteCommandInDatabase(dropCommand);
+    }
+
+    private void ExecuteCommandInDatabase(SqlCommand command)
+    {
+        string? originalDatabase = DatabaseName == command.Connection.Database ? null : command.Connection.Database;
+
         try
         {
             if (originalDatabase is not null)
             {
-                Connection.ChangeDatabase(_databaseName);
+                command.Connection.ChangeDatabase(DatabaseName);
             }
 
-            dropCommand.ExecuteNonQuery();
+            command.ExecuteNonQuery();
         }
         finally
         {
             if (originalDatabase is not null)
             {
-                Connection.ChangeDatabase(originalDatabase);
+                command.Connection.ChangeDatabase(originalDatabase);
             }
         }
     }

src/Microsoft.Data.SqlClient/tests/Common/Fixtures/DatabaseObjects/ServerLogin.cs

@@ -7,9 +7,9 @@ namespace Microsoft.Data.SqlClient.Tests.Common.Fixtures.DatabaseObjects;
 /// <summary>
 /// A transient server login, created at the start of its scope and dropped when disposed.
 /// </summary>
-public sealed class ServerLogin : DatabaseObject
+public sealed class ServerLogin : DatabaseObject<string>
 {
-    public string Password { get; }
+    public string Password => State;
 
     /// <summary>
     /// Initializes a new instance of the ServerLogin class using the specified SQL connection, login name prefix, and default database.
@@ -24,9 +24,8 @@ public ServerLogin(SqlConnection connection, string namePrefix, string? defaultD
     }
 
     private ServerLogin(SqlConnection connection, string namePrefix, string password, string? defaultDatabase)
-        : base(connection, namePrefix, GenerateDefinition(password, defaultDatabase), shouldCreate: true, shouldDrop: true)
+        : base(connection, namePrefix, GenerateDefinition(password, defaultDatabase), password, shouldCreate: true, shouldDrop: true)
     {
-        Password = password;
     }
 
     private static string GenerateDefinition(string password, string? defaultDatabase) =>