Use same exception type when conversion fails.

This improves compatibility with Connector/NET.

Signed-off-by: Bradley Grainger <[email protected]>

Author: bgrainger

src/MySqlConnector/MySql.Data.Types/MySqlConversionException.cs

@@ -0,0 +1,12 @@
+using System;
+
+namespace MySql.Data.Types
+{
+	public class MySqlConversionException : Exception
+	{
+		public MySqlConversionException(string message)
+			: base(message)
+		{
+		}
+	}
+}

src/MySqlConnector/MySql.Data.Types/MySqlDateTime.cs

@@ -48,7 +48,7 @@ public int Millisecond
 		}
 
 		public DateTime GetDateTime() =>
-			!IsValidDateTime ? throw new InvalidOperationException("Cannot convert to DateTime when IsValidDateTime is false.") :
+			!IsValidDateTime ? throw new MySqlConversionException("Cannot convert MySqlDateTime to DateTime when IsValidDateTime is false.") : 
 				new DateTime(Year, Month, Day, Hour, Minute, Second, DateTimeKind.Unspecified).AddTicks(Microsecond * 10);
 
 		public override string ToString() => IsValidDateTime ? GetDateTime().ToString() : "0000-00-00";

tests/MySqlConnector.Tests/MySqlDateTimeTests.cs

@@ -51,6 +51,14 @@ public void GetDateTime()
 			Assert.Equal(new DateTime(2018, 6, 9, 12, 34, 56, 123).AddTicks(4560), dt);
 		}
 
+		[Fact]
+		public void GetDateTimeForInvalidDate()
+		{
+			var msdt = new MySqlDateTime();
+			Assert.False(msdt.IsValidDateTime);
+			Assert.Throws<MySqlConversionException>(() => msdt.GetDateTime());
+		}
+
 		[Fact]
 		public void SetMicrosecond()
 		{