[英]Use lambda function in new switch c# 8.0 to return value
I want to use new switch in my code, that for method result make log and return IActionResult
.我想在我的代码中使用新的开关,方法结果 make log 并返回IActionResult
。
I try to do something like this:我尝试做这样的事情:
var response = (this._coreRepository.Write(value.Content, data.Id.ToString())); \\return bool
return response switch
{
true => () =>
{
this._log.LogInformation("Write is complited");
return Ok();
},
false => () =>
{
this._log.LogInformation("Error in writing");
return BadRequest();
},
_ => () =>
{
throw new Exception("Unexpected error");
}
};
But compiler says to me cannot convert lambda expression to type 'IActionResult' because it is not a delegate type
.但是编译器对我说cannot convert lambda expression to type 'IActionResult' because it is not a delegate type
。
How can I fix it?我该如何解决?
The problem is that your switch expression returns a lambda expression
but the containing method expects IActionResult
.问题是您的 switch 表达式返回lambda expression
,但包含方法需要IActionResult
。 To fix the problem you should rewrite the return statement to immediately invoke result of the switch expression:要解决此问题,您应该重写 return 语句以立即调用 switch 表达式的结果:
var response = (this._coreRepository.Write(value.Content, data.Id.ToString()));
return (response switch
{
// Here we cast lambda expression to Func<IActionResult> so that compiler
// can define the type of the switch expression as Func<IActionResult>.
true => (Func<IActionResult>) (() =>
{
this._log.LogInformation("Write is complited");
return Ok();
}),
false => () =>
{
this._log.LogInformation("Error in writing");
return BadRequest();
},
_ => () =>
{
throw new Exception("Unexpected error");
}
})(); // () - here we invoke Func<IActionResult>, the result of the switch expression.
If I were you I would rewrite this code the next way to make it easier to read:如果我是你,我会用下一种方式重写这段代码,使其更易于阅读:
var response = (this._coreRepository.Write(value.Content, data.Id.ToString()));
// Now additional braces or casts are not required.
Func<IActionResult> func = response switch
{
true => () =>
{
this._log.LogInformation("Write is complited");
return Ok();
},
false => () =>
{
this._log.LogInformation("Error in writing");
return BadRequest();
},
_ => () =>
{
throw new Exception("Unexpected error");
}
}
return func();
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