diff --git a/AicsKnowledgeBase_file/Controllers/FileController.cs b/AicsKnowledgeBase_file/Controllers/FileController.cs
index ebfc64e..25b9804 100644
--- a/AicsKnowledgeBase_file/Controllers/FileController.cs
+++ b/AicsKnowledgeBase_file/Controllers/FileController.cs
@@ -44,13 +44,17 @@ public class FileController : ControllerBase {
 
     [HttpPost]
     public async Task<IActionResult> UploadFilePart(string fileId, [FromForm] UploadFileDto dto) {
-        var metadata = await _knowledgeFileHandler.GetFileMetadata(fileId);
-        if (metadata.Ticket != dto.Ticket) {
-            return this.ProblemFromCode(ErrorCodes.TicketMismatch);
-        }
+        try {
+            var metadata = await _knowledgeFileHandler.GetFileMetadata(fileId);
+            if (metadata.Ticket != dto.Ticket) {
+                return this.ProblemFromCode(ErrorCodes.TicketMismatch);
+            }
 
-        await _knowledgeFileHandler.SaveFileSlice(fileId, dto.File, dto.RangeStart, dto.RangeEnd);
-        return Ok();
+            await _knowledgeFileHandler.SaveFileSlice(fileId, dto.File, dto.RangeStart, dto.RangeEnd);
+            return Ok();
+        } catch (FileNotFoundException e) {
+            return Problem(statusCode: StatusCodes.Status404NotFound, title: e.Message);
+        }
     }
 
     [HttpPost("complete")]
diff --git a/AicsKnowledgeBase_file/Handlers/KnowledgeFileHandler.cs b/AicsKnowledgeBase_file/Handlers/KnowledgeFileHandler.cs
index fd92ed7..88d5b29 100644
--- a/AicsKnowledgeBase_file/Handlers/KnowledgeFileHandler.cs
+++ b/AicsKnowledgeBase_file/Handlers/KnowledgeFileHandler.cs
@@ -85,10 +85,10 @@ public class KnowledgeFileHandler {
 
     public async Task<Memory<byte>> ReadRanged(string fileId, ulong rangeStart, ulong rangeEnd) {
         var metadata = await GetFileMetadata(fileId);
-        var fileStream = File.OpenRead(GetFileName(fileId, metadata.Suffix));
+        await using var fileStream = File.OpenRead(GetFileName(fileId, metadata.Suffix));
         var buffer = new Memory<byte>(new byte[rangeEnd - rangeStart]);
+        fileStream.Seek((long)rangeStart, SeekOrigin.Begin);
         await fileStream.ReadExactlyAsync(buffer);
-        fileStream.Close();
         return buffer;
     }
 }
\ No newline at end of file
diff --git a/FileServerTests/UnitTest1.cs b/FileServerTests/UnitTest1.cs
index 212ef9b..3554f59 100644
--- a/FileServerTests/UnitTest1.cs
+++ b/FileServerTests/UnitTest1.cs
@@ -15,7 +15,17 @@ public class UnitTest1 {
         // Console.WriteLine("--- 127.0.0.1:8090 ---");
 
         // var resp = await client.GetAsync("https://127.0.0.1:8090/hello");
-        var resp = await client.GetAsync("https://api.hammer-hfut.tk:233/aics/file/hello");
+        var content = new MultipartFormDataContent();
+        content.Add(new StringContent("$5$mq5AaInP$veRAiN732QWi0JIChKnFpArb8LqvJJMBn4t/QBf4DB."), "ticket");
+        content.Add(new StringContent("149"), "rangeStart");
+        content.Add(new StringContent("297"), "rangeEnd");
+        content.Add(
+            new StreamContent(File.OpenRead(@"C:\Users\arnor\Downloads\auto组第二次汇报.pptx")), 
+            "file", 
+            "file.txt"
+            );
+        var resp = await client.PostAsync("https://api.hammer-hfut.tk:233/aics/file/File/8d7c236a-9518-4b57-a143-3fe040cf7954", content);
+        // var resp = await client.PostAsync("https://127.0.0.1:8081/File/8d7c236a-9518-4b57-a143-3fe040cf7954", content);
         var headers = new StringBuilder();
         foreach (var (headerName, headerValues) in resp.Headers) {
             headers.AppendLine($"{headerName}: {string.Join(", ", headerValues)}");