新增GroupByIF的重载方法

Src/Asp.NetCore2/SqlSugar/Abstract/QueryableProvider/QueryableProvider.cs

@@ -1078,6 +1078,18 @@ namespace SqlSugar
             }
             return this;
         }
+
+        public ISugarQueryable<T> GroupByIF(bool isGroupBy, string groupFields)
+        {
+            if (isGroupBy)
+            {
+                GroupBy(groupFields);
+            }
+
+            return this;
+        }
+
+
         public virtual ISugarQueryable<T> OrderByIF(bool isOrderBy, string orderFileds)
         {
             if (isOrderBy)

Src/Asp.NetCore2/SqlSugar/Interface/IQueryable.cs

@@ -117,6 +117,8 @@ namespace SqlSugar
         ISugarQueryable<T> GroupBy(string groupFileds);
         ISugarQueryable<T> GroupByIF(bool isGroupBy, Expression<Func<T, object>> expression);
 
+        ISugarQueryable<T> GroupByIF(bool isGroupBy, string groupFields);
+
         ISugarQueryable<T> PartitionBy(Expression<Func<T, object>> expression);
         ISugarQueryable<T> PartitionBy(string groupFileds);