Update vor Umbau Service

API_NetFramework/Helper/Helper.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Globalization;
 using System.Linq;
 using System.Text;
 using System.Web;
@@ -40,5 +41,49 @@ namespace OnDocAPI_NetFramework.Helper
 
             return lowerCase ? builder.ToString().ToLower() : builder.ToString();
         }
+
+        public static string NormalizeDateToSystemFormat(string input)
+        {
+            if (string.IsNullOrWhiteSpace(input))
+                return input;
+
+            var culture = CultureInfo.CurrentCulture;
+
+            string[] knownFormats =
+            {
+            "yyyy-MM-dd",
+            "yyyyMMdd",
+            "dd.MM.yyyy",
+            "d.M.yyyy",
+            "dd/MM/yyyy",
+            "MM/dd/yyyy",
+            "yyyy-MM-ddTHH:mm:ss",
+            "yyyy-MM-dd HH:mm:ss",
+            "dd.MM.yyyy HH:mm:ss",
+            "d.M.yyyy HH:mm:ss"
+        };
+
+            DateTime date;
+
+            // 1. Exakte Formate
+            if (DateTime.TryParseExact(
+                    input.Trim(),
+                    knownFormats,
+                    culture,
+                    DateTimeStyles.AllowWhiteSpaces | DateTimeStyles.AssumeLocal,
+                    out date))
+            {
+                return date.ToString(culture.DateTimeFormat.ShortDatePattern, culture);
+            }
+
+            // 2. Fallback: freie Erkennung
+            if (DateTime.TryParse(input, culture, DateTimeStyles.AssumeLocal, out date))
+            {
+                return date.ToString(culture.DateTimeFormat.ShortDatePattern, culture);
+            }
+
+            return input;
+        }
     }
+
 }