Initial commit

RequiredValidationRule.cs

@@ -0,0 +1,25 @@
+using System.Globalization;
+using System.Windows.Controls;
+
+namespace ChrisKaczor.Wpf.Validation
+{
+    public class RequiredValidationRule : ValidationRule
+    {
+        public static string GetErrorMessage(object? fieldValue)
+        {
+            var errorMessage = string.Empty;
+
+            if (fieldValue == null || string.IsNullOrWhiteSpace(fieldValue.ToString()))
+                errorMessage = "Required";
+
+            return errorMessage;
+        }
+
+        public override ValidationResult Validate(object value, CultureInfo cultureInfo)
+        {
+            var error = GetErrorMessage(value);
+
+            return !string.IsNullOrEmpty(error) ? new ValidationResult(false, error) : ValidationResult.ValidResult;
+        }
+    }
+}