问用于检查x是否以y开头的字符串的IComparer

EN

Dim query = From str In array Where str.StartsWith("prefix")

query = array.Where(Function(str) str.StartsWith("prefix"))

var query = array.Where(s => s.StartsWith("prefix"));

class StartsWithComparer : IComparer<string>
{
    public int Compare(string a, string b) {
        if(a.StartsWith(b)) {
            return 0;
        }
        return a.CompareTo(b);
    }
}

IEnumerable<string> GetBefore(IList<string> sorted, int foundIndex, string prefix) {
    for(var i = foundIndex - 1; i >= 0; i--) {
        if(sorted[i].StartsWith(prefix)) {
            yield return sorted[i];
        }
    }
}

IEnumerable<string> GetCurrentAndAfter(IList<string> sorted, int foundIndex, string prefix) {
    for(var i = foundIndex; i < sorted.Count; i++) {
        if(sorted[i].StartsWith(prefix)) {
            yield return sorted[i];
        }
    }
}

var index = sorted.BinarySearch("asdf", new StartsWithComparer());
var previous = GetBefore(sorted, index, "asdf");
var currentAndAfter = GetCurrentAndAfter(sorted, index, "asdf");