It imposible get index value when iterate over button element with a @onclick function

[Ksantacr]

Describe the bug

Is not possible to get index value on iteration over button element

To Reproduce

1. Open Visual Studio Community 2019
2. Create Blazor WebAssembly App (with default settings)
3. On Index.razor after SurveyPrompt component add:

<ol>
    @for (int i = 0; i < list.Count() - 1; i++)
    {
        <li>
            <button @onclick=@(() =>Call(i))>
                item # @i
            </button>
        </li>
    }
</ol>
<button @onclick=AddItem>
    Add item
</button>

@code {
    List<string[]> list = new List<string[]>();
    private void AddItem()
    {
        string[] l = new string[9];
        list.Add(l);
    }
    private void Call(int i)
    {
        Console.WriteLine(i);
    }
}

4. Click Add Item button, 4 times
5. Click whatever button with Call (item # 1) function.
6. I excepted if I click on Item#0 it sends me 0, but it sends the current size of List

Further technical details

• ASP.NET Core version
  5.0.100-preview.3.20216.6
• Include the output of dotnet --info

SDK de .NET Core (reflejando cualquier global.json):
 Version:   5.0.100-preview.3.20216.6
 Commit:    9f62a32109

Entorno de tiempo de ejecución:
 OS Name:     Windows
 OS Version:  10.0.18362
 OS Platform: Windows
 RID:         win10-x64
 Base Path:   C:\Program Files\dotnet\sdk\5.0.100-preview.3.20216.6\

Host (useful for support):
  Version: 5.0.0-preview.3.20214.6
  Commit:  b037784658

.NET SDKs installed:
  2.1.802 [C:\Program Files\dotnet\sdk]
  2.2.402 [C:\Program Files\dotnet\sdk]
  3.1.100 [C:\Program Files\dotnet\sdk]
  3.1.302 [C:\Program Files\dotnet\sdk]
  3.1.400-preview-015178 [C:\Program Files\dotnet\sdk]
  5.0.100-preview.3.20216.6 [C:\Program Files\dotnet\sdk]

.NET runtimes installed:
  Microsoft.AspNetCore.All 2.1.13 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.1.16 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.1.20 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.2.7 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.App 2.1.13 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.1.16 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.1.20 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.2.7 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 3.1.0 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 3.1.2 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 3.1.6 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 5.0.0-preview.3.20215.14 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 2.1.13 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.1.16 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.1.20 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.2.7 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 3.1.0 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 3.1.2 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 3.1.6 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 5.0.0-preview.3.20214.6 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.WindowsDesktop.App 3.1.0 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 3.1.2 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 3.1.6 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 5.0.0-preview.3.20214.2 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

• The IDE (VS / VS Code/ VS4Mac) you're running on, and it's version

Visual Studio Community 2019 Version 16.6.5

[mrpmorris]

This is just the way C# works. The loop variable is not captured so always comes out with the same value.

To solve it either so a foreach over Enumberable.Range, or inside your loop capture the value to a local variable and use that instead.

for (int i, etc)
{
  int currentIndex = i;
  etc
} 

[Ksantacr]

This is just the way C# works. The loop variable is not captured so always comes out with the same value.

To solve it either so a foreach over Enumberable.Range, or inside your loop capture the value to a local variable and use that instead.

for (int i, etc)
{
  int currentIndex = i;
  etc
} 

Thanks solved, but I need to catch the value inside the loop.

Where I Can find information about this C# issue?

[mrpmorris]

What is it doing now you've added the suggested change, and what would you like it to do instead?

[ghost]

This issue has been resolved and has not had any activity for 1 day. It will be closed for housekeeping purposes.

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