优化打印预览窗口的参数生成逻辑，支持根据合并字段顺序生成相应的 JSON 数据，增强打印模板的灵活性和可定制性。同时，修复了列级合并逻辑，确保在处理重复键时不会抛出异常。

yy-admin-master/YY.Admin.Services/Service/Print/NativePrintRenderService.cs

@@ -1017,14 +1017,18 @@ public static class NativePrintRenderService
         var colList = columns.OfType<JsonObject>().ToList();
         if (mergeColumnKeys.Length > 0)
         {
-            var byKey = colList.ToDictionary(
-                c => ReadAsString(c["key"]) ?? string.Empty,
-                c => ReadAsString(c["bindField"]) ?? ReadAsString(c["field"]) ?? string.Empty);
+            // 用 GroupBy 兜底，避免重复 key 抛异常；按 mergeColumnKeys 给定顺序输出对应 bindField/field
+            var byKey = colList
+                .GroupBy(c => ReadAsString(c["key"]) ?? string.Empty)
+                .ToDictionary(
+                    g => g.Key,
+                    g => ReadAsString(g.First()["bindField"]) ?? ReadAsString(g.First()["field"]) ?? string.Empty);
             return mergeColumnKeys
                 .Select(k => byKey.TryGetValue(k, out var f) ? f : string.Empty)
                 .Where(f => !string.IsNullOrEmpty(f))
                 .ToList();
         }
+        // 兼容老的列级 mergeByValue 开关
         return colList
             .Where(c => string.Equals(ReadAsString(c["mergeByValue"]), "true", StringComparison.OrdinalIgnoreCase))
             .Select(c => ReadAsString(c["bindField"]) ?? ReadAsString(c["field"]) ?? string.Empty)