what does [parameter] before method means?[Answered] RSS

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  behzad.sdghi

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  5 Points

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  what does [parameter] before method means?

  May 29, 2020 03:35 AM|behzad.sdghi|LINK

  what does [parameter] before method means?

• • Reply
  Tsaisoul

  Member

  10 Points

  13 Posts

  Re: what does [parameter] before method means?

  May 29, 2020 05:15 AM|Tsaisoul|LINK

  The attribute before the method has many usages,they can provide a way of associating information with code in a declarative way. They can also provide a reusable element that can be applied to a variety of targets.

  What they mean depends on your method and what you want to do

  For example,[AcceptVerbs("GET", "POST")] can make the method support both get and post.

   [AcceptVerbs("GET", "POST")]
          public IActionResult VerifyEmail([RegularExpression("^[a-zA-Z0-9_\\.-]+@([a-zA-Z0-9-]+\\.)+[a-zA-Z]{2,6}$")] string email)
          {
              if (!ModelState.IsValid) 
                  return Json($"Don't use {email},change a form right now!");
             else
                  return Json(true);
  
          }

  or it can be used to get the parmeter from the models.

  [HttpGet("{id}")]
          public ActionResult<Pet> GetById(int id, bool dogsOnly)
          #endregion
          {
              var pet = _petsInMemoryStore.FirstOrDefault(
                  p => p.Id == id &&
                  (!dogsOnly || p.PetType == PetType.Dog));
  
              if (pet == null)
              {
                  return NotFound();
              }
  
              return pet;
          }

  you can search the official tutorial , they are useful,https://docs.microsoft.com/en-us/dotnet/csharp/tutorials/attributes

• • Reply
  Rena Ni

  Contributor

  2690 Points

  874 Posts

  Re: what does [parameter] before method means?

  May 29, 2020 05:45 AM|Rena Ni|LINK

  Hi behzad.sdghi,

  Did you use blazor?

  [Parameter] is used to mark the component parameters that can be set when the component is used in another page.

  Reference:

  https://docs.microsoft.com/en-us/aspnet/core/blazor/components?view=aspnetcore-3.1#component-parameters

  For more detailed exlpanation,in this code below:

  <div class="panel panel-default">
      <div class="panel-heading">@Title</div>
      <div class="panel-body">@ChildContent</div>
  
      <button class="btn btn-primary" @onclick="OnClick">
          Trigger a Parent component method
      </button>
  </div>
  
  @code {
      public string Title { get; set; }
  
      public RenderFragment ChildContent { get; set; }
  
      public EventCallback<MouseEventArgs> OnClick { get; set; }
  }

  If you do not add [Parameter] attribute, those are just public properties that can't be set from other pages.That is to say the following line would be invalid :

  <ChildComponent Title="Panel Title from Parent" />
  

  The correct way should be:

  <div class="panel panel-default">
      <div class="panel-heading">@Title</div>
      <div class="panel-body">@ChildContent</div>
  
      <button class="btn btn-primary" @onclick="OnClickCallback">
          Trigger a Parent component method
      </button>
  </div>
  
  @code {
      [Parameter]
      public string Title { get; set; }
  
      [Parameter]
      public RenderFragment ChildContent { get; set; }
  
      [Parameter]
      public EventCallback<MouseEventArgs> OnClickCallback { get; set; }
  }

  Then it allows you could set the parameters whenever we use that component:

  <ChildComponent Title="Panel Title from Parent"
                  OnClickCallback="@ShowMessage">
      Content of the child component is supplied
      by the parent component.
  </ChildComponent>

  Best Regards,

  Rena

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• • Reply
  PaulTheSmith

  Participant

  1620 Points

  927 Posts

  Re: what does [parameter] before method means?

  May 29, 2020 05:45 AM|PaulTheSmith|LINK

  If, when you say [parameter] you actually mean [Parameter]

  and when you say 'method' you mean 'property'

  then this page may help https://docs.microsoft.com/en-us/aspnet/core/blazor/components?view=aspnetcore-3.1&viewFallbackFrom=aspnetcore-3.0#component-parameters

  If my assumptions are not correct can you show the code where this attribute is used?' 

• • Reply
  Evern

  Member

  80 Points

  32 Posts

  Re: what does [parameter] before method means?

  May 29, 2020 05:47 AM|Evern|LINK

  Hi,

  I don't know where you use this parameter, if you use this parameter in blazor it means binding routing parameter or other in-page data, [parameter] is essential.

  Regards,

  Evern