The following C# solution to the Valid Parentheses question causes a compilation error on the web editor, but it compiles fine on Rider.

using System.Collections.Generic;

public class Solution {
    public bool IsValid(string s) {
        var stack = new Stack<char>();
        foreach (var c in s)
        {
            if (IsClosingBracket(c))
            {
                var previous = stack.Pop();
                var expectedBracket = GetCorrespondingOpeningBracket(c);
                if (!expectedBracket.HasValue) return false;
                if (previous != expectedBracket.Value)
                {
                    return false;
                }
            }
            else 
            {
                stack.Push(c);
            }
        }
        return stack.Count == 0;
    }

    private char? GetCorrespondingOpeningBracket(char c)
    {
        return c switch {
            ')' => '(',
            ']' => '[',
            '}' => '{',
            _ => null
        };
    }

    private bool IsClosingBracket(char c)
    {
        return c switch
        {
            ')' => true,
            ']' => true,
            '}' => true,
            _ => false
        };
    }
}

causes the following compilation error

MSBuild version 17.7.1+971bf70db for .NET
Determining projects to restore...
Restored /box/Main.csproj (in 36 ms).
/box/Main.cs(0,22): error CS1513: } expected [/box/Main.csproj]
/box/Main.cs(1,5): error CS1529: A using clause must precede all other elements defined in the namespace except extern alias declarations [/box/Main.csproj]
/box/Main.cs(48,5): error CS8803: Top-level statements must precede namespace and type declarations. [/box/Main.csproj]
/box/Main.cs(48,5): error CS0106: The modifier 'public' is not valid for this item [/box/Main.csproj]
/box/Main.cs(69,5): error CS0106: The modifier 'public' is not valid for this item [/box/Main.csproj]
/box/Main.cs(80,5): error CS0106: The modifier 'public' is not valid for this item [/box/Main.csproj]
/box/Main.cs(87,1): error CS1022: Type or namespace definition, or end-of-file expected [/box/Main.csproj]

Build FAILED.

/box/Main.cs(0,22): error CS1513: } expected [/box/Main.csproj]
/box/Main.cs(1,5): error CS1529: A using clause must precede all other elements defined in the namespace except extern alias declarations [/box/Main.csproj]
/box/Main.cs(48,5): error CS8803: Top-level statements must precede namespace and type declarations. [/box/Main.csproj]
/box/Main.cs(48,5): error CS0106: The modifier 'public' is not valid for this item [/box/Main.csproj]
/box/Main.cs(69,5): error CS0106: The modifier 'public' is not valid for this item [/box/Main.csproj]
/box/Main.cs(80,5): error CS0106: The modifier 'public' is not val...
output limit exceeded