/Clip the elevation layer with water body
string out_workspace = Project.Current.DefaultGeodatabasePath;
string input_feature = Path.Combine(out_workspace, strFeature1);

string input_data = Path.Combine(out_workspace, strDEM1);
string out_data = Path.Combine(out_workspace, "Water_Temp1");

// make a value array of strings to be passed to ExecuteToolAsync
var parameters = Geoprocessing.MakeValueArray(input_data, "", out_data, input_feature, "", "ClippingGeometry", "MAINTAIN_EXTENT");

// execute the tool
Geoprocessing.ExecuteToolAsync("management.Clip", parameters, null, null, null, GPExecuteToolFlags.None);