fix(csharp/src/Client): Fix some resource management in AdbcDataReader (#4134)

Fixes a few small issues I noticed while reviewing a change recently.

Author: CurtHagenlocher

csharp/src/Client/AdbcDataReader.cs

@@ -134,13 +134,7 @@ private RecordBatch RecordBatch
 
         public override void Close()
         {
-            if (this.closeConnection)
-            {
-                this.adbcCommand?.Connection?.Close();
-            }
-            this.adbcQueryResult.Stream?.Dispose();
-            this.adbcQueryResult.Stream = null;
-            this.isClosed = true;
+            this.Dispose(disposing: true);
         }
 
         public override bool GetBoolean(int ordinal)
@@ -308,22 +302,23 @@ public override bool IsDBNull(int ordinal)
 
         public override bool NextResult()
         {
-            this.recordBatch = ReadNextRecordBatchAsync().Result;
-
-            if (this.recordBatch != null)
-            {
-                return true;
-            }
-
             return false;
         }
 
         protected override void Dispose(bool disposing)
         {
             if (disposing)
             {
+                if (this.closeConnection)
+                {
+                    this.adbcCommand?.Connection?.Close();
+                }
+
                 this.recordBatch?.Dispose();
                 this.recordBatch = null;
+                this.adbcQueryResult.Stream?.Dispose();
+                this.adbcQueryResult.Stream = null;
+                this.isClosed = true;
             }
         }
 
@@ -339,6 +334,7 @@ public override bool Read()
             // If ReadNextRecordBatchAsync throws (e.g. server error mid-stream),
             // callers that retry Read() must not re-read stale rows from the
             // old batch — they must see the exception again immediately.
+            this.recordBatch?.Dispose();
             this.recordBatch = null;
             this.recordBatch = ReadNextRecordBatchAsync().Result;
 

csharp/test/Apache.Arrow.Adbc.Tests/Client/DuckDbClientTests.cs

@@ -139,13 +139,16 @@ public void BindParameters()
             command.Parameters[1].DbType = DbType.String;
             command.Parameters[1].Value = "foo";
 
-            using var reader = command.ExecuteReader();
-            long count = 0;
-            while (reader.Read())
+            using (var reader = command.ExecuteReader(CommandBehavior.CloseConnection))
             {
-                count++;
+                long count = 0;
+                while (reader.Read())
+                {
+                    count++;
+                }
+                Assert.Equal(1, count);
             }
-            Assert.Equal(1, count);
+            Assert.True(connection.State == ConnectionState.Closed);
         }
 
         private static long GetResultCount(AdbcCommand command, string query)