Fix bug with LegacyRowVersionNullBehavior (#1182)

Author: cheenamalhotra

src/Microsoft.Data.SqlClient/netcore/src/Microsoft/Data/SqlClient/SqlDataReader.cs

@@ -842,7 +842,7 @@ protected override void Dispose(bool disposing)
                 }
                 base.Dispose(disposing);
             }
-            catch(SqlException ex)
+            catch (SqlException ex)
             {
                 SqlClientEventSource.Log.TryTraceEvent("SqlDataReader.Dispose | ERR | Error Message: {0}, Stack Trace: {1}", ex.Message, ex.StackTrace);
             }
@@ -3771,26 +3771,18 @@ private bool TryReadColumnInternal(int i, bool readHeaderOnly = false)
                     _sharedState._nextColumnDataToRead = _sharedState._nextColumnHeaderToRead;
                     _sharedState._nextColumnHeaderToRead++;  // We read this one
 
-                    if (isNull)
+                    // Trigger new behavior for RowVersion to send DBNull.Value by allowing entry for Timestamp or discard entry for Timestamp for legacy support.
+                    // if LegacyRowVersionNullBehavior is enabled, Timestamp type must enter "else" block.
+                    if (isNull && (!LocalAppContextSwitches.LegacyRowVersionNullBehavior || columnMetaData.type != SqlDbType.Timestamp))
                     {
-                        if (columnMetaData.type == SqlDbType.Timestamp)
-                        {
-                            if (!LocalAppContextSwitches.LegacyRowVersionNullBehavior)
-                            {
-                                _data[i].SetToNullOfType(SqlBuffer.StorageType.SqlBinary);
-                            }
-                        }
-                        else
-                        {
-                            TdsParser.GetNullSqlValue(_data[_sharedState._nextColumnDataToRead],
+                        TdsParser.GetNullSqlValue(_data[_sharedState._nextColumnDataToRead],
                                 columnMetaData,
                                 _command != null ? _command.ColumnEncryptionSetting : SqlCommandColumnEncryptionSetting.UseConnectionSetting,
                                 _parser.Connection);
 
-                            if (!readHeaderOnly)
-                            {
-                                _sharedState._nextColumnDataToRead++;
-                            }
+                        if (!readHeaderOnly)
+                        {
+                            _sharedState._nextColumnDataToRead++;
                         }
                     }
                     else
@@ -4102,8 +4094,8 @@ internal bool TrySetMetaData(_SqlMetaDataSet metaData, bool moreInfo)
 
                     if (_parser != null)
                     { // There is a valid case where parser is null
-                        // Peek, and if row token present, set _hasRows true since there is a
-                        // row in the result
+                      // Peek, and if row token present, set _hasRows true since there is a
+                      // row in the result
                         byte b;
                         if (!_stateObj.TryPeekByte(out b))
                         {
@@ -5015,7 +5007,7 @@ override public Task<T> GetFieldValueAsync<T>(int i, CancellationToken cancellat
                     {
                         _stateObj._shouldHaveEnoughData = true;
 #endif
-                    return Task.FromResult(GetFieldValueInternal<T>(i));
+                        return Task.FromResult(GetFieldValueInternal<T>(i));
 #if DEBUG
                     }
                     finally
@@ -5109,7 +5101,7 @@ internal void CompletePendingReadWithFailure(int errorCode, bool resetForcePendi
 
 #endif
 
-        internal abstract class SqlDataReaderAsyncCallContext<T> : AAsyncCallContext<SqlDataReader,T>
+        internal abstract class SqlDataReaderAsyncCallContext<T> : AAsyncCallContext<SqlDataReader, T>
         {
             internal static readonly Action<Task<T>, object> s_completeCallback = CompleteAsyncCallCallback;
 

src/Microsoft.Data.SqlClient/netcore/src/Microsoft/Data/SqlClient/TdsParser.cs

@@ -5424,6 +5424,10 @@ internal static object GetNullSqlValue(SqlBuffer nullVal, SqlMetaDataPriv md, Sq
                     break;
 
                 case SqlDbType.Timestamp:
+                    if (!LocalAppContextSwitches.LegacyRowVersionNullBehavior)
+                    {
+                        nullVal.SetToNullOfType(SqlBuffer.StorageType.SqlBinary);
+                    }
                     break;
 
                 default:

src/Microsoft.Data.SqlClient/netfx/src/Microsoft/Data/SqlClient/SqlDataReader.cs

@@ -4281,26 +4281,18 @@ private bool TryReadColumnInternal(int i, bool readHeaderOnly = false)
                     _sharedState._nextColumnDataToRead = _sharedState._nextColumnHeaderToRead;
                     _sharedState._nextColumnHeaderToRead++;  // We read this one
 
-                    if (isNull)
+                    // Trigger new behavior for RowVersion to send DBNull.Value by allowing entry for Timestamp or discard entry for Timestamp for legacy support.
+                    // if LegacyRowVersionNullBehavior is enabled, Timestamp type must enter "else" block.
+                    if (isNull && (!LocalAppContextSwitches.LegacyRowVersionNullBehavior || columnMetaData.type != SqlDbType.Timestamp))
                     {
-                        if (columnMetaData.type == SqlDbType.Timestamp)
-                        {
-                            if (!LocalAppContextSwitches.LegacyRowVersionNullBehavior)
-                            {
-                                _data[i].SetToNullOfType(SqlBuffer.StorageType.SqlBinary);
-                            }
-                        }
-                        else
-                        {
-                            TdsParser.GetNullSqlValue(_data[_sharedState._nextColumnDataToRead],
+                        TdsParser.GetNullSqlValue(_data[_sharedState._nextColumnDataToRead],
                                 columnMetaData,
                                 _command != null ? _command.ColumnEncryptionSetting : SqlCommandColumnEncryptionSetting.UseConnectionSetting,
                                 _parser.Connection);
 
-                            if (!readHeaderOnly)
-                            {
-                                _sharedState._nextColumnDataToRead++;
-                            }
+                        if (!readHeaderOnly)
+                        {
+                            _sharedState._nextColumnDataToRead++;
                         }
                     }
                     else

src/Microsoft.Data.SqlClient/netfx/src/Microsoft/Data/SqlClient/TdsParser.cs

@@ -6208,8 +6208,10 @@ internal static object GetNullSqlValue(
                     break;
 
                 case SqlDbType.Timestamp:
-                    // Dev10 Bug #479607 - this should have been the same as SqlDbType.Binary, but it's a rejected breaking change
-                    // Dev10 Bug #752790 - don't assert when it does happen
+                    if (!LocalAppContextSwitches.LegacyRowVersionNullBehavior)
+                    {
+                        nullVal.SetToNullOfType(SqlBuffer.StorageType.SqlBinary);
+                    }
                     break;
 
                 default: