定制代码契约异常消息 [英] Customising Code Contract Exception Messages

问题描述

我有一个代码表示的合同，因为这 - 它验证被存储的实体不为空，有效期为持久性。有用。 。FAB

I have a code contract expresses as this - it validates that entity to be stored is not null and is valid for persistence. It works. Fab.

[ContractClassFor(typeof(IRepository<,>))]
internal abstract class ContractsForIRepository<T, TId> : IRepository<T, TId> where T : IEntity
{
    private ContractsForIRepository()
    {

    } 

    public T Persist(T entity)
    {
        Contract.Requires<InvalidEntityException>(entity != null, "Entity is null");
        Contract.Requires<InvalidEntityException>(entity.IsValidForPersistence(), "Entity not valid for persistence");
        return default(T);
    }

}

不过，我想例外更有用 - 因为任何人都接收该消息会想知道什么实体是无效的，什么是样子。所有实体重写的ToString（），所以我想包括此错误消息：

However, I would like the exception to be more useful - as anyone receiving the message will want to know what entity was invalid and what is looked like. All of the entities override ToString(), so I wanted to include this in the error message:

Contract.Requires<InvalidEntityException>(entity.IsValidForPersistence(), "Entity not valid for persistence " + entity.ToString());

我已经包含的ToString是明确的 - 这将是隐式调用，如果我忽略它，但我认为它使我的问题更加清晰。

I have included ToString to be explicit - it would be called implicitly if I omitted it, but I think it makes my question clearer.

现在的问题是，这不是由合约代码允许，我得到以下信息。

The problem is, this isn't allowed by code contracts and I get the following message.

网友留言合同通话只能是字符串文字或静态字段或静态属性，至少是内部可见。

User message to contract call can only be string literal, or a static field, or static property that is at least internally visible.

有什么办法，包括在异常消息的具体数据？

Is there any way to include specific data in the exception message?

推荐答案

据文档：

2.10重载合同法

所有的合同方法具有重载一个字符串在
除了布尔条件：

All of the contract methods have overloads that take a string in addition to the boolean condition:

Contract.Requires（X =空，如果x为null，则导弹！是红色的！）;

用户提供的字符串将显示只要合同是在运行时违反了
。 目前，它必须是一个编译时常

The user-supplied string will be displayed whenever the contract is violated at runtime. Currently, it must be a compile-time constant.

所以，你问是不可能的

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