private string GetPreSignStr(SortedDictionary<string, string> inputPara)
{
Dictionary<string, string> sPara = new Dictionary<string, string>();
//过滤空值、sign与sign_type参数
sPara = Core.FilterPara(inputPara);
//获取待签名字符串
string preSignStr = Core.CreateLinkString(sPara);
return preSignStr;
}