try this code.hope it will help.
string content = "Shoes|plant|tree|usek|setan|babi|anjing";
string keyword = @"^shoes\|plant";
string result="";
if (Regex.Match(content, keyword, RegexOptions.Singleline | RegexOptions.IgnoreCase).Success)
{
result = Regex.Match(content, keyword, RegexOptions.Singleline | RegexOptions.IgnoreCase).ToString();
}