dotnetcore#549-Excel中缺少列时，应返回空和错误，不应该空指针异常

src/Magicodes.ExporterAndImporter.Core/Models/ImportResult.cs

@@ -23,6 +23,7 @@ public class ImportResultEnumer<T> where T : class
         /// </summary>
         public ImportResultEnumer()
         {
+            Data = new List<T>();
             RowErrors = new List<DataRowErrorInfo>();
         }
 
@@ -70,6 +71,7 @@ public class ImportResult<T> where T : class
         /// </summary>
         public ImportResult()
         {
+            Data = new List<T>();
             RowErrors = new List<DataRowErrorInfo>();
         }
 

src/Magicodes.ExporterAndImporter.Tests/ExcelImporter_Tests.cs

@@ -1210,5 +1210,15 @@ public async Task Issue377_Test()
             import.HasError.ShouldBeFalse();
             import.Data.Count.ShouldBe(3);
         }
+
+        [Fact(DisplayName = "#549-Excel中缺少列时，应返回空和错误，不应该空指针异常")]
+        public async Task MissingField_Test()
+        {
+            var filePath = Path.Combine(Directory.GetCurrentDirectory(), "TestFiles", "Import", "Issue549.xlsx");
+            var import = await Importer.Import<Issue549>(filePath);
+
+            import.HasError.ShouldBeTrue();
+            import.Data.Count.ShouldBe(0);
+        }
     }
 }

src/Magicodes.ExporterAndImporter.Tests/Models/Import/Issue549.cs

@@ -0,0 +1,15 @@
+using Magicodes.ExporterAndImporter.Core;
+
+namespace Magicodes.IE.Tests.Models.Import;
+
+public class Issue549
+{
+    [ImporterHeader(Name = "姓名", AutoTrim = true)]
+    public string Name { get; set; }
+
+    [ImporterHeader(Name = "年龄", AutoTrim = true)]
+    public decimal Age { get; set; }
+
+    [ImporterHeader(Name = "身高", AutoTrim = true)]
+    public decimal Height { get; set; }
+}