Calls in SetWarningProperties() have allocation overhead due to multiple enumeration

[Erarndt]

SetWarningProperties() has the following implementation:

private static void SetWarningProperties(IObjectWriter writer, ProjectRestoreMetadata msbuildMetadata)
{
    if (msbuildMetadata.ProjectWideWarningProperties != null &&
        (msbuildMetadata.ProjectWideWarningProperties.AllWarningsAsErrors ||
         msbuildMetadata.ProjectWideWarningProperties.NoWarn.Count > 0 ||
         msbuildMetadata.ProjectWideWarningProperties.WarningsAsErrors.Count > 0))
    {
        writer.WriteObjectStart("warningProperties");

        SetValueIfTrue(writer, "allWarningsAsErrors", msbuildMetadata.ProjectWideWarningProperties.AllWarningsAsErrors);

        if (msbuildMetadata.ProjectWideWarningProperties.NoWarn.Count > 0)
        {
            SetArrayValue(writer, "noWarn", msbuildMetadata
               .ProjectWideWarningProperties
               .NoWarn
               .ToArray()
               .OrderBy(c => c)
               .Select(c => c.GetName())
               .Where(c => !string.IsNullOrEmpty(c)));
        }

        if (msbuildMetadata.ProjectWideWarningProperties.WarningsAsErrors.Count > 0)
        {
            SetArrayValue(writer, "warnAsError", msbuildMetadata
                .ProjectWideWarningProperties
                .WarningsAsErrors
                .ToArray()
                .OrderBy(c => c)
                .Select(c => c.GetName())
                .Where(c => !string.IsNullOrEmpty(c)));
        }

        if (msbuildMetadata.ProjectWideWarningProperties.WarningsNotAsErrors.Count > 0)
        {
            SetArrayValue(writer, "warnNotAsError", msbuildMetadata
                .ProjectWideWarningProperties
                .WarningsNotAsErrors
                .ToArray()
                .OrderBy(c => c)
                .Select(c => c.GetName())
                .Where(c => !string.IsNullOrEmpty(c)));
        }

        writer.WriteObjectEnd();
    }
}

There are three calls to SetArrayValue() that get passed a chain of Linq calls. SetArrayValue() has this implementation:

private static void SetArrayValue(IObjectWriter writer, string name, IEnumerable<string> values)
{
    if (values != null && values.Any())
    {
        writer.WriteNameArray(name, values);
    }
}

The intent is that the array is only written if values is not empty. A consequence of the current implementation is that there is some non-trivial work that is duplicated since there is multiple enumeration happening:

From the trace you can see that the Any() call requires us to repeat all the work after the ToArray() call until the enumerator gets an item. For OrderBy() this requires consuming the entire enumerable and allocating the intermediate arrays that will hold the sorted items. The code should be restructured to avoid the multiple enumeration.

[ghost]

Issue is missing Type label, remember to add a Type label