add empty constructor #69

Author: 喻斌

src/CatLib.Core/Support/Stream/CombineStream.cs

@@ -17,7 +17,7 @@ namespace CatLib
     /// <summary>
     /// 组合流，允许将多个不同的流组合成一个流
     /// </summary>
-    public class CombineStream : Stream
+    public class CombineStream : WrapperStream
     {
         /// <summary>
         /// 全局游标位置

src/CatLib.Core/Support/Stream/WrapperStream.cs

@@ -54,6 +54,14 @@ public override long Position
         /// </summary>
         public override long Length => BaseStream.Length;
 
+        /// <summary>
+        /// 构建一个包装流
+        /// </summary>
+        public WrapperStream()
+        {
+            BaseStream = this;
+        }
+
         /// <summary>
         /// 构建一个包装流
         /// </summary>