CSHARP-595: corrected issue with infinite recursion when converting a BsonValue to another BsonValue.

Bson/ObjectModel/BsonValue.cs

@@ -1543,7 +1543,7 @@ namespace MongoDB.Bson
                 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.ObjectId: return Convert.ChangeType(this.AsObjectId, conversionType, provider);
                 case BsonType.String: return Convert.ChangeType(this.AsString, conversionType, provider);
                 default: throw new InvalidCastException();
             }

Bson/ObjectModel/ObjectId.cs

@@ -29,7 +29,7 @@ namespace MongoDB.Bson
     /// Represents an ObjectId (see also BsonObjectId).
     /// </summary>
     [Serializable]
-    public struct ObjectId : IComparable<ObjectId>, IEquatable<ObjectId>
+    public struct ObjectId : IComparable<ObjectId>, IEquatable<ObjectId>, IConvertible
     {
         // private static fields
         private static ObjectId __emptyInstance = default(ObjectId);
@@ -464,5 +464,107 @@ namespace MongoDB.Bson
         {
             return BsonUtils.ToHexString(Pack(_timestamp, _machine, _pid, _increment));
         }
+
+        // explicit IConvertible implementation
+        TypeCode IConvertible.GetTypeCode()
+        {
+            return TypeCode.Object;
+        }
+
+        bool IConvertible.ToBoolean(IFormatProvider provider)
+        {
+            throw new InvalidCastException();
+        }
+
+        byte IConvertible.ToByte(IFormatProvider provider)
+        {
+            throw new InvalidCastException();
+        }
+
+        char IConvertible.ToChar(IFormatProvider provider)
+        {
+            throw new InvalidCastException();
+        }
+
+        DateTime IConvertible.ToDateTime(IFormatProvider provider)
+        {
+            throw new InvalidCastException();
+        }
+
+        decimal IConvertible.ToDecimal(IFormatProvider provider)
+        {
+            throw new InvalidCastException();
+        }
+
+        double IConvertible.ToDouble(IFormatProvider provider)
+        {
+            throw new InvalidCastException();
+        }
+
+        short IConvertible.ToInt16(IFormatProvider provider)
+        {
+            throw new InvalidCastException();
+        }
+
+        int IConvertible.ToInt32(IFormatProvider provider)
+        {
+            throw new InvalidCastException();
+        }
+
+        long IConvertible.ToInt64(IFormatProvider provider)
+        {
+            throw new InvalidCastException();
+        }
+
+        sbyte IConvertible.ToSByte(IFormatProvider provider)
+        {
+            throw new InvalidCastException();
+        }
+
+        float IConvertible.ToSingle(IFormatProvider provider)
+        {
+            throw new InvalidCastException();
+        }
+
+        string IConvertible.ToString(IFormatProvider provider)
+        {
+            return ToString();
+        }
+
+        object IConvertible.ToType(Type conversionType, IFormatProvider provider)
+        {
+            switch (Type.GetTypeCode(conversionType))
+            {
+                case TypeCode.String:
+                    return ((IConvertible)this).ToString(provider);
+                case TypeCode.Object:
+                    if (conversionType == typeof(BsonObjectId))
+                    {
+                        return new BsonObjectId(this);
+                    }
+                    if (conversionType == typeof(BsonString))
+                    {
+                        return new BsonString(((IConvertible)this).ToString(provider));
+                    }
+                    break;
+            }
+
+            throw new InvalidCastException();
+        }
+
+        ushort IConvertible.ToUInt16(IFormatProvider provider)
+        {
+            throw new InvalidCastException();
+        }
+
+        uint IConvertible.ToUInt32(IFormatProvider provider)
+        {
+            throw new InvalidCastException();
+        }
+
+        ulong IConvertible.ToUInt64(IFormatProvider provider)
+        {
+            throw new InvalidCastException();
+        }
     }
 }

BsonUnitTests/BsonUnitTests.csproj

@@ -115,6 +115,7 @@
     <Compile Include="IO\BsonDocumentWriterTests.cs" />
     <Compile Include="IO\JsonReaderTests.cs" />
     <Compile Include="IO\JsonScannerTests.cs" />
+    <Compile Include="Jira\CSharp595Tests.cs" />
     <Compile Include="Jira\CSharp102Tests.cs" />
     <Compile Include="Jira\CSharp104Tests.cs" />
     <Compile Include="Jira\CSharp116Tests.cs" />

BsonUnitTests/Jira/CSharp595Tests.cs

@@ -0,0 +1,56 @@
+/* Copyright 2010-2012 10gen Inc.
+*
+* Licensed under the Apache License, Version 2.0 (the "License");
+* you may not use this file except in compliance with the License.
+* You may obtain a copy of the License at
+*
+* http://www.apache.org/licenses/LICENSE-2.0
+*
+* Unless required by applicable law or agreed to in writing, software
+* distributed under the License is distributed on an "AS IS" BASIS,
+* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+* See the License for the specific language governing permissions and
+* limitations under the License.
+*/
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using NUnit.Framework;
+
+using MongoDB.Bson;
+using MongoDB.Bson.Serialization;
+
+namespace MongoDB.BsonUnitTests.Jira.CSharp595
+{
+    [TestFixture]
+    public class CSharp595Tests
+    {
+        [Test]
+        public void TestDoesNotThrowStackOverflowExceptionWhenConvertingToSelfType()
+        {
+            BsonObjectId id1 = BsonObjectId.GenerateNewId();
+            BsonObjectId id2 = null;
+            Assert.DoesNotThrow(() =>
+            {
+                id2 = (BsonObjectId)((IConvertible)id1).ToType(typeof(BsonObjectId), null);
+            });
+
+            Assert.AreEqual(id1, id2);
+        }
+
+        [Test]
+        public void TestDoesNotThrowStackOverflowExceptionWhenConvertingToBsonString()
+        {
+            BsonObjectId id1 = BsonObjectId.GenerateNewId();
+            BsonString id2 = null;
+            Assert.DoesNotThrow(() =>
+            {
+                id2 = (BsonString)((IConvertible)id1).ToType(typeof(BsonString), null);
+            });
+
+            Assert.AreEqual(id1.ToString(), id2.AsString);
+        }
+    }
+}