How to Use ArcMap Buffer tool in c#

public static void MakeBufferLayer(string inputFeatureclasspath, string outputFeatureclassPath, string buffer_distance_or_field)
        {
            Geoprocessor GP = new Geoprocessor();
            GP.OverwriteOutput = true;
            GP.AddOutputsToMap = false;
            ESRI.ArcGIS.AnalysisTools.Buffer bufferTool = new
              ESRI.ArcGIS.AnalysisTools.Buffer();

            bufferTool.in_features = inputFeatureclasspath;
            bufferTool.out_feature_class = outputFeatureclassPath;// outputFeatureclassPath;
            bufferTool.buffer_distance_or_field = buffer_distance_or_field;

            try
            {
                GP.Execute(bufferTool, null);
            }
            catch (Exception e)
            {
                MessageBox.Show(ErrorMessages.GetErrorByCode(137)+" "+ErrorMessages.GetErrorByCode(100),"Error",MessageBoxButtons.OK,MessageBoxIcon.Error);
            }
        }