rename Preconditions to GrpcPreconditions
diff --git a/src/csharp/Grpc.IntegrationTesting/ClientRunners.cs b/src/csharp/Grpc.IntegrationTesting/ClientRunners.cs
index e9e659c..5e91d4a 100644
--- a/src/csharp/Grpc.IntegrationTesting/ClientRunners.cs
+++ b/src/csharp/Grpc.IntegrationTesting/ClientRunners.cs
@@ -58,7 +58,7 @@
         public static IClientRunner CreateStarted(ClientConfig config)
         {
             string target = config.ServerTargets.Single();
-            Grpc.Core.Utils.Preconditions.CheckArgument(config.LoadParams.LoadCase == LoadParams.LoadOneofCase.ClosedLoop);
+            GrpcPreconditions.CheckArgument(config.LoadParams.LoadCase == LoadParams.LoadOneofCase.ClosedLoop);
 
             var credentials = config.SecurityParams != null ? TestCredentials.CreateSslCredentials() : ChannelCredentials.Insecure;
             var channel = new Channel(target, credentials);
@@ -95,7 +95,7 @@
         
         public SyncUnaryClientRunner(Channel channel, int payloadSize, HistogramParams histogramParams)
         {
-            this.channel = Grpc.Core.Utils.Preconditions.CheckNotNull(channel);
+            this.channel = GrpcPreconditions.CheckNotNull(channel);
             this.payloadSize = payloadSize;
             this.histogram = new Histogram(histogramParams.Resolution, histogramParams.MaxPossible);