ArcEngine 调用加权叠加GP服务输入栅格参数

ArcEngine 调用WeightedSum加权叠加GP服务输入栅格参数如何写？
//初始化GP服务
Geoprocessor GP = new Geoprocessor();
GP.OverwriteOutput = true;
WeightedSum weightSum = new WeightedSum();
weightSum.in_rasters = “”；这里的in_rasters如何写啊