moving from Yavsc main lib

Yavsc.Server/Attributes/Validation/YaRequiredAttribute.cs

@@ -0,0 +1,37 @@
+using System;
+
+namespace Yavsc.Attributes.Validation
+{
+    [AttributeUsage(AttributeTargets.Property | AttributeTargets.Field | AttributeTargets.Parameter, AllowMultiple = false)]
+    public class YaRequiredAttribute : YaValidationAttribute
+    {
+
+        /// <summary>
+        /// Gets or sets a flag indicating whether the attribute should allow empty strings.
+        /// </summary>
+        public bool AllowEmptyStrings { get; set; }
+         public YaRequiredAttribute (string msg) : base()
+         {
+             ErrorMessage = msg;
+         } 
+        public YaRequiredAttribute () 
+        {
+            this.ErrorMessage = ResourcesHelpers.GlobalLocalizer["RequiredField"];
+            
+        }
+        public override bool IsValid(object value) {
+            if (value == null) {
+                return false;
+            }
+
+            // only check string length if empty strings are not allowed
+            var stringValue = value as string;
+            if (stringValue != null && !AllowEmptyStrings) {
+                return stringValue.Trim().Length != 0;
+            }
+
+            return true;
+        }
+    }
+    
+}