Fix behavior when removing values/keys from DapperRow

Dapper/SqlMapper.cs

@@ -1319,10 +1319,22 @@ public DapperRow(DapperTable table, object[] values)
                 this.table = table;
                 this.values = values;
             }
-
-            int ICollection<KeyValuePair<string,object>>.Count
+            private sealed class DeadValue
+            {
+                public static readonly DeadValue Default = new DeadValue();
+                private DeadValue() { }
+            }
+            int ICollection<KeyValuePair<string, object>>.Count
             {
-                get { return table.FieldCount; }
+                get
+                {
+                    int count = 0;
+                    for (int i = 0; i < values.Length; i++)
+                    {
+                        if (!(values[i] is DeadValue)) count++;
+                    }
+                    return count;
+                }
             }
 
             public bool TryGetValue(string name, out object value)
@@ -1335,40 +1347,24 @@ public bool TryGetValue(string name, out object value)
                 }
                 // exists, **even if** we don't have a value; consider table rows heterogeneous
                 value = index < values.Length ? values[index] : null;
+                if (value is DeadValue)
+                { // pretend it isn't here
+                    value = null;
+                    return false;
+                }
                 return true;
             }
 
-            /* public object SetValue(string name, object value)
-            {
-                var index = Table.IndexOfName(name);
-                if (index == -1)
-                {
-                    if (m_additionalValues == null)
-                    {
-                        m_additionalValues = new Dictionary<string, object>();
-                    }
-
-                    m_additionalValues[name ?? ""] = value;
-                    return value;
-                }
-
-                return SetFieldValueImpl(index, value);
-            }*/
-
             public override string ToString()
             {
                 var sb = new StringBuilder("{DapperRow");
-
                 foreach (var kv in this)
                 {
                     var value = kv.Value;
-                    sb.Append(", ");
-                    sb.Append(kv.Key);
+                    sb.Append(", ").Append(kv.Key);
                     if (value != null)
                     {
-                        sb.Append(" = '");
-                        sb.Append(kv.Value);
-                        sb.Append('\'');
+                        sb.Append(" = '").Append(kv.Value).Append('\'');
                     }
                     else
                     {
@@ -1376,11 +1372,11 @@ public override string ToString()
                     }
                 }
 
-                sb.Append('}');
-                return sb.ToString();
+                return sb.Append('}').ToString();
             }
 
-            public System.Dynamic.DynamicMetaObject GetMetaObject(System.Linq.Expressions.Expression parameter)
+            System.Dynamic.DynamicMetaObject System.Dynamic.IDynamicMetaObjectProvider.GetMetaObject(
+                System.Linq.Expressions.Expression parameter)
             {
                 return new DapperRowMetaObject(parameter, System.Dynamic.BindingRestrictions.Empty, this);
             }
@@ -1391,7 +1387,10 @@ public System.Dynamic.DynamicMetaObject GetMetaObject(System.Linq.Expressions.Ex
                 for (var i = 0; i < names.Length; i++)
                 {
                     object value = i < values.Length ? values[i] : null;
-                    yield return new KeyValuePair<string, object>(names[i], value);
+                    if (!(value is DeadValue))
+                    {
+                        yield return new KeyValuePair<string, object>(names[i], value);
+                    }
                 }
             }
 
@@ -1410,7 +1409,8 @@ IEnumerator IEnumerable.GetEnumerator()
 
             void ICollection<KeyValuePair<string, object>>.Clear()
             { // removes values for **this row**, but doesn't change the fundamental table
-                values = new object[0];
+                for (int i = 0; i < values.Length; i++)
+                    values[i] = DeadValue.Default;
             }
 
             bool ICollection<KeyValuePair<string, object>>.Contains(KeyValuePair<string, object> item)
@@ -1444,7 +1444,9 @@ IEnumerator IEnumerable.GetEnumerator()
 
             bool IDictionary<string, object>.ContainsKey(string key)
             {
-                return table.FieldExists(key);
+                int index = table.IndexOfName(key);
+                if (index < 0 || index >= values.Length || values[index] is DeadValue) return false;
+                return true;
             }
 
             void IDictionary<string, object>.Add(string key, object value)
@@ -1456,8 +1458,9 @@ IEnumerator IEnumerable.GetEnumerator()
             bool IDictionary<string, object>.Remove(string key)
             {
                 int index = table.IndexOfName(key);
-                if(index >= 0 && index < values.Length) values[index] = null;
-                return index >= 0;                
+                if (index < 0 || index >= values.Length || values[index] is DeadValue) return false;
+                values[index] = DeadValue.Default;
+                return true;
             }
 
             object IDictionary<string, object>.this[string key]
@@ -1478,7 +1481,7 @@ public object SetValue(string key, object value)
                     // grow it to the full width of the table
                     Array.Resize(ref values, table.FieldCount);
                 }
-                return values[index] = value;              
+                return values[index] = value;
             }
 
             ICollection<string> IDictionary<string, object>.Keys

Tests/Tests.cs

@@ -2127,7 +2127,18 @@ public void TestDynamicMutation()
             var obj = connection.Query("select 1 as [a], 2 as [b], 3 as [c]").Single();
             ((int)obj.a).IsEqualTo(1);
             IDictionary<string,object> dict = obj;
-            dict.Remove("a");
+            Assert.Equals(3, dict.Count);
+            Assert.IsTrue(dict.Remove("a"));
+            Assert.IsFalse(dict.Remove("d"));
+            Assert.Equals(2, dict.Count);
+            dict.Add("d", 4);
+            Assert.Equals(3, dict.Count);
+            Assert.Equals("b,c,d", string.Join(",", dict.Keys.OrderBy(x => x)));
+            Assert.Equals("2,3,4", string.Join(",", dict.OrderBy(x => x.Key).Select(x => x.Value)));
+
+            Assert.Equals(2, (int)obj.b);
+            Assert.Equals(3, (int)obj.c);
+            Assert.Equals(4, (int)obj.d);
             try
             {
                 ((int)obj.a).IsEqualTo(1);