Serialize enums as string when type is MySqlDbType.String. Fixes #459

Author: Naragato

src/MySqlConnector/MySql.Data.MySqlClient/MySqlParameter.cs

@@ -303,6 +303,10 @@ internal void AppendSqlString(BinaryWriter writer, StatementPreparerOptions opti
 			{
 				writer.WriteUtf8("{0}".FormatInvariant((ulong) Value));
 			}
+			else if ((MySqlDbType == MySqlDbType.String || MySqlDbType == MySqlDbType.VarChar) && HasSetDbType && Value is Enum)
+			{
+				writer.WriteUtf8("'{0:G}'".FormatInvariant(Value));
+			}
 			else if (Value is Enum)
 			{
 				writer.WriteUtf8("{0:d}".FormatInvariant(Value));

tests/MySqlConnector.Tests/DummyEnum.cs

@@ -0,0 +1,8 @@
+namespace MySqlConnector.Tests
+{
+	internal enum DummyEnum
+	{
+		FirstValue,
+		SecondValue
+	} 
+}

tests/MySqlConnector.Tests/StatementPreparerTests.cs

@@ -30,6 +30,28 @@ public void ParametersIgnoredInComments(string sql)
 			Assert.Equal(sql, GetParsedSql(sql));
 		}
 
+		[Theory]
+		[InlineData(MySqlDbType.String, DummyEnum.FirstValue, "'FirstValue'")]
+		[InlineData(MySqlDbType.VarChar, DummyEnum.FirstValue, "'FirstValue'")]
+		[InlineData(null, DummyEnum.FirstValue, "0")]
+		public void EnumParametersAreParsedCorrectly(MySqlDbType? type, object value, string replacedValue)
+		{
+			const string sql = "SELECT @param";
+			var parameters = new MySqlParameterCollection();
+			var paramater = new MySqlParameter("@param", value);
+
+			if (type != null)
+			{
+				paramater.MySqlDbType = type.Value;
+			}
+
+			parameters.Add(paramater);
+			
+			var parsedSql = GetParsedSql(sql, parameters);
+			Assert.Equal(sql.Replace("@param", replacedValue), parsedSql);
+
+		}
+
 		[Theory]
 		[InlineData("SELECT '@param';")]
 		[InlineData("SELECT \"@param\";")]

tests/SideBySide/InsertTests.cs

@@ -249,6 +249,37 @@ public void InsertEnumValue()
 			Assert.Equal(Enum64.On, results[1].Enum64);
 		}
 
+		[Fact]
+		public async Task EnumParametersAreParsedCorrectly()
+		{
+			await m_database.Connection.ExecuteAsync(@"drop table if exists insert_enum_value2;
+create table insert_enum_value2(rowid integer not null primary key auto_increment, `Varchar` varchar(10), `String` varchar(10), `Int` int null);");
+
+			try
+			{
+				await m_database.Connection.OpenAsync();
+				using (var command = new MySqlCommand("INSERT INTO insert_enum_value2 (`Varchar`, `String`, `Int`) VALUES (@Varchar, @String, @Int);", m_database.Connection))
+				{
+
+					command.Parameters.Add(new MySqlParameter("@String", MySqlColor.Orange)).MySqlDbType = MySqlDbType.String;
+					command.Parameters.Add(new MySqlParameter("@Varchar", MySqlColor.Green)).MySqlDbType = MySqlDbType.VarChar;
+					command.Parameters.Add(new MySqlParameter("@Int", MySqlColor.None));
+
+					await command.ExecuteNonQueryAsync();
+					var result = (await m_database.Connection.QueryAsync<ColorEnumValues>(@"select `Varchar`, `String`, `Int` from insert_enum_value2;")).ToArray();
+					Assert.Single(result);
+					Assert.Equal(MySqlColor.Orange.ToString("G"), result[0].String);
+					Assert.Equal(MySqlColor.Green.ToString("G"), result[0].Varchar);
+					Assert.Equal((int) MySqlColor.None, result[0].Int);
+				}
+			}
+			finally
+			{
+				m_database.Connection.Close();
+			}
+
+		}
+
 		enum Enum16 : short
 		{
 			Off,
@@ -272,6 +303,12 @@ class DateTimeOffsetValues
 			public DateTimeOffset? datetimeoffset1 { get; set; }
 		}
 
+		class ColorEnumValues
+		{
+			public string Varchar { get; set; }
+			public string String { get; set; }
+			public int Int { get; set; }
+		}
 
 		class EnumValues
 		{