Remove a couple LINQ usages in Microsoft.Extensions

[eerhardt]

Note that this was the only usage of Enumerable.Cast in a Blazor WASM default app. So this allows for that method to be trimmed. It is also faster and allocates less according to this benchmark:

    [MemoryDiagnoser]
    public class JoinBenchmark
    {
        private const string NullValue = "(null)";
        private static IEnumerable s_Enumerable = Enumerable.Range(1, 10);

        [Benchmark]
        public string OldWay()
        {
            return string.Join(", ", s_Enumerable.Cast<object>().Select(o => o ?? NullValue));
        }

        [Benchmark]
        public string NewWay()
        {
            var vsb = new ValueStringBuilder(stackalloc char[256]);
            bool first = true;
            foreach (object e in s_Enumerable)
            {
                if (!first)
                {
                    vsb.Append(", ");
                }

                vsb.Append(e != null ? e.ToString() : NullValue);
                first = false;
            }
            return vsb.ToString();
        }
    }

Method	Mean	Error	StdDev	Gen 0	Gen 1	Gen 2	Allocated
OldWay	468.1 ns	3.29 ns	2.92 ns	0.0798	-	-	504 B
NewWay	222.2 ns	2.72 ns	2.27 ns	0.0621	-	-	392 B

[ghost]

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Issue Details

---

Note that this was the only usage of Enumerable.Cast in a Blazor WASM default app. So this allows for that method to be trimmed. It is also faster and allocates less according to this benchmark:

    [MemoryDiagnoser]
    public class JoinBenchmark
    {
        private const string NullValue = "(null)";
        private static IEnumerable s_Enumerable = Enumerable.Range(1, 10);

        [Benchmark]
        public string OldWay()
        {
            return string.Join(", ", s_Enumerable.Cast<object>().Select(o => o ?? NullValue));
        }

        [Benchmark]
        public string NewWay()
        {
            var vsb = new ValueStringBuilder(stackalloc char[256]);
            bool first = true;
            foreach (object e in s_Enumerable)
            {
                if (!first)
                {
                    vsb.Append(", ");
                }

                vsb.Append(e != null ? e.ToString() : NullValue);
                first = false;
            }
            return vsb.ToString();
        }
    }

Method	Mean	Error	StdDev	Gen 0	Gen 1	Gen 2	Allocated
OldWay	468.1 ns	3.29 ns	2.92 ns	0.0798	-	-	504 B
NewWay	222.2 ns	2.72 ns	2.27 ns	0.0621	-	-	392 B

Author:	eerhardt
Assignees:	-
Labels:	area-Extensions-Configuration
Milestone:	-

[maryamariyan]

LGTM, Aside from the error:

src/libraries/Microsoft.Extensions.Configuration.Xml/src/XmlStreamConfigurationProvider.cs(76,88): error CS1061: (NETCORE_ENGINEERING_TELEMETRY=Build) 'Stack<string>' does not contain a definition for 'Reverse' and no accessible extension method 'Reverse' accepting a first argument of type 'Stack<string>' could be found (are you missing a using directive or an assembly reference?)

[ghost]

Hello @eerhardt!

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