ArcEngine中调用Near服务总是没有效果

调用ArcEngine中的Near服务总是没有效果，gp_Near.ExecuteAsync(pNear)这句话好像是多线程执行，程序运行没有出错，但是结果一直不出来，一直也没有找到解决办法。ArcEngine里面怎么那么多GP服务调用不成功呢，感觉有些懵逼啊，有时候看了好多网上的资料也没有找到好的解决办法呀。。。。。
 /// <summary>
/// 调用GP临近分析服务
/// </summary>
/// <param name="inputfeature"></param>
/// <param name="nearfeature"></param>
/// <param name="search_radius"></param>
public void GP_Near(string inputfeature, string nearfeature, string search_radius,string location,string angle)
{
Geoprocessor gp_Near = new Geoprocessor();
gp_Near.OverwriteOutput = true;
ESRI.ArcGIS.AnalysisTools.Near pNear = new ESRI.ArcGIS.AnalysisTools.Near();
pNear.in_features = inputfeature;
pNear.near_features = nearfeature;
pNear.search_radius = search_radius;
pNear.location = location;
pNear.angle = angle;
gp_Near.ExecuteAsync(pNear);
}