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//------------------------------------------------------------
// Copyright (c) Microsoft Corporation. All rights reserved.
//------------------------------------------------------------
namespace System.ServiceModel
{
using System.Collections.Generic;
using System.IdentityModel;
// Embed this struct in a class to represent a field of that class
// that is logically a list, but contains just one item in all but
// the rarest of scenarios. When this class must be passed around
// in internal APIs, use it as a ref parameter.
struct MostlySingletonList<T> where T : class
{
int count;
T singleton;
List<T> list;
public T this[int index]
{
get
{
if (this.list == null)
{
EnsureValidSingletonIndex(index);
return this.singleton;
}
else
{
return this.list[index];
}
}
}
public int Count
{
get { return this.count; }
}
public void Add(T item)
{
if (this.list == null)
{
if (this.count == 0)
{
this.singleton = item;
this.count = 1;
return;
}
this.list = new List<T>();
this.list.Add(this.singleton);
this.singleton = null;
}
this.list.Add(item);
this.count++;
}
static bool Compare(T x, T y)
{
return x == null ? y == null : x.Equals(y);
}
public bool Contains(T item)
{
return IndexOf(item) >= 0;
}
void EnsureValidSingletonIndex(int index)
{
if (this.count != 1 || index != 0)
{
throw DiagnosticUtility.ExceptionUtility.ThrowHelperError(new ArgumentOutOfRangeException("index"));
}
}
bool MatchesSingleton(T item)
{
return this.count == 1 && Compare(this.singleton, item);
}
public int IndexOf(T item)
{
if (this.list == null)
{
return MatchesSingleton(item) ? 0 : -1;
}
else
{
return this.list.IndexOf(item);
}
}
public bool Remove(T item)
{
if (this.list == null)
{
if (MatchesSingleton(item))
{
this.singleton = null;
this.count = 0;
return true;
}
else
{
return false;
}
}
else
{
bool result = this.list.Remove(item);
if (result)
{
this.count--;
}
return result;
}
}
public void RemoveAt(int index)
{
if (this.list == null)
{
EnsureValidSingletonIndex(index);
this.singleton = null;
this.count = 0;
}
else
{
this.list.RemoveAt(index);
this.count--;
}
}
}
}
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