Implemented CSHARP-496. The BsonValue implementation of IConvertible.ToString can now convert BsonObjectIds to string.

Author: rstam

Bson/ObjectModel/BsonValue.cs

@@ -1528,6 +1528,7 @@ string IConvertible.ToString(IFormatProvider provider)
                 case BsonType.Double: return Convert.ToString(this.AsDouble, provider);
                 case BsonType.Int32: return Convert.ToString(this.AsInt32, provider);
                 case BsonType.Int64: return Convert.ToString(this.AsInt64, provider);
+                case BsonType.ObjectId: return this.AsObjectId.ToString();
                 case BsonType.String: return this.AsString;
                 default: throw new InvalidCastException();
             }
@@ -1542,6 +1543,7 @@ object IConvertible.ToType(Type conversionType, IFormatProvider provider)
                 case BsonType.Double: return Convert.ChangeType(this.AsDouble, conversionType, provider);
                 case BsonType.Int32: return Convert.ChangeType(this.AsInt32, conversionType, provider);
                 case BsonType.Int64: return Convert.ChangeType(this.AsInt64, conversionType, provider);
+                case BsonType.ObjectId: return Convert.ChangeType(this, conversionType, provider);
                 case BsonType.String: return Convert.ChangeType(this.AsString, conversionType, provider);
                 default: throw new InvalidCastException();
             }

BsonUnitTests/ObjectModel/BsonValueIConvertibleTests.cs

@@ -306,7 +306,7 @@ public void TestBsonNull()
         [Test]
         public void TestBsonObjectId()
         {
-            var value = BsonObjectId.Empty;
+            var value = new BsonObjectId(ObjectId.Parse("0102030405060708090a0b0c"));
             Assert.Throws<InvalidCastException>(() => Convert.ToBoolean(value));
             Assert.Throws<InvalidCastException>(() => Convert.ToByte(value));
             Assert.Throws<InvalidCastException>(() => Convert.ToChar(value));
@@ -318,7 +318,8 @@ public void TestBsonObjectId()
             Assert.Throws<InvalidCastException>(() => Convert.ToInt64(value));
             Assert.Throws<InvalidCastException>(() => Convert.ToSByte(value));
             Assert.Throws<InvalidCastException>(() => Convert.ToSingle(value));
-            Assert.Throws<InvalidCastException>(() => Convert.ToString(value));
+            Assert.AreEqual("0102030405060708090a0b0c", Convert.ToString(value));
+            Assert.AreEqual("0102030405060708090a0b0c", ((IConvertible)value).ToType(typeof(string), null));
             Assert.Throws<InvalidCastException>(() => Convert.ToUInt16(value));
             Assert.Throws<InvalidCastException>(() => Convert.ToUInt32(value));
             Assert.Throws<InvalidCastException>(() => Convert.ToUInt64(value));