C# 为什么NUnit'；s Assert.That（..）有ref重载？

也许我只是在装傻，但你什么时候为什么要用：

NUnit.Framework.Assert.That<T>(ref T, NUnit.Framework.Constraints.IResolveConstraint, string, params object[])
NUnit.Framework.Assert.That<T>(ref T, NUnit.Framework.Constraints.IResolveConstraint, string)
NUnit.Framework.Assert.That<T>(ref T, NUnit.Framework.Constraints.IResolveConstraint)

---

通过ref传递给这些方法带来了什么好处？

深入研究NUnit源代码，我发现：

static public void That<T>(ref T actual, IResolveConstraint expression, string message, params object[] args)
{
    Constraint constraint = expression.Resolve();

    Assert.IncrementAssertCount();
    if (!constraint.Matches(ref actual))
    {
        MessageWriter writer = new TextMessageWriter(message, args);
        constraint.WriteMessageTo(writer);
        throw new AssertionException(writer.ToString());
    }
}

    public virtual bool Matches<T>(ref T actual)
    {
        return Matches(actual);
    }

正如您所看到的，在实现上没有区别。

Ref T actual

重载允许您将值类型作为引用传递，而引用类型已经作为引用传递

static public void That<T>(ref T actual, IResolveConstraint expression, string message, params object[] args)
{
    Constraint constraint = expression.Resolve();

    Assert.IncrementAssertCount();
    if (!constraint.Matches(ref actual))
    {
        MessageWriter writer = new TextMessageWriter(message, args);
        constraint.WriteMessageTo(writer);
        throw new AssertionException(writer.ToString());
    }
}

    public virtual bool Matches<T>(ref T actual)
    {
        return Matches(actual);
    }

    static public void That(object actual, IResolveConstraint expression, string message, params object[] args)
    {
        Constraint constraint = expression.Resolve();

        Assert.IncrementAssertCount();
        if (!constraint.Matches(actual))
        {
            MessageWriter writer = new TextMessageWriter(message, args);
            constraint.WriteMessageTo(writer);
            throw new AssertionException(writer.ToString());
        }
    }