diff --git a/Validation/AlphanumericAttribute.cs b/Validation/AlphanumericAttribute.cs
new file mode 100644
index 0000000..58ce175
--- /dev/null
+++ b/Validation/AlphanumericAttribute.cs
@@ -0,0 +1,13 @@
+
+using System.ComponentModel.DataAnnotations;
+using System.Numerics;
+using System.Text;
+using System.Text.RegularExpressions;
+
+namespace NejCommon.Validation;
+
+public class AlphanumericAttribute : RegexAttribute{
+    public AlphanumericAttribute() : base("^[a-zA-Z0-9]*$","Aabb123"){
+
+    }
+}
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diff --git a/Validation/IbanAttribute.cs b/Validation/IbanAttribute.cs
new file mode 100644
index 0000000..f8a188e
--- /dev/null
+++ b/Validation/IbanAttribute.cs
@@ -0,0 +1,50 @@
+
+using System.ComponentModel.DataAnnotations;
+using System.Numerics;
+using System.Text;
+using System.Text.RegularExpressions;
+
+namespace NejCommon.Validation;
+
+public class IbanAttribute : RegexAttribute{
+    public const string IbanRegex = @"^[A-Z]{2}\d{2}[A-Z0-9]{11,30}$";
+    public IbanAttribute() : base(IbanRegex,"CZ4622500000000104816258"){
+
+    }
+
+    protected override ValidationResult IsValid(object value, ValidationContext ctx)
+    {
+        if (value is null)
+            return ValidationResult.Success!;
+        var res = base.IsValid(value, ctx);
+        if (res != ValidationResult.Success)
+            return res;
+        
+        string iban = value as string;
+
+        string rearranged = iban.Substring(4) + iban.Substring(0, 4);
+
+        // Convert letters to numbers (A=10, B=11, ..., Z=35)
+        StringBuilder numericIban = new StringBuilder();
+        foreach (char ch in rearranged)
+        {
+            if (char.IsLetter(ch))
+            {
+                int charVal = ch - 'A' + 10;
+                numericIban.Append(charVal);
+            }
+            else
+            {
+                numericIban.Append(ch);
+            }
+        }
+
+        // Convert to BigInteger and compute mod 97
+        BigInteger ibanNumber = BigInteger.Parse(numericIban.ToString());
+
+        if(ibanNumber % 97 == 1)
+            return ValidationResult.Success;
+        else
+            return new ValidationResult("Invalid checksum of IBAN");
+    }
+}
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diff --git a/Validation/NejValidationAttribute.cs b/Validation/NejValidationAttribute.cs
new file mode 100644
index 0000000..cc96731
--- /dev/null
+++ b/Validation/NejValidationAttribute.cs
@@ -0,0 +1,19 @@
+
+
+using System.ComponentModel.DataAnnotations;
+using Microsoft.OpenApi.Models;
+
+namespace NejCommon.Validation;
+
+[AttributeUsage(AttributeTargets.Property, AllowMultiple = false)]
+public abstract class NejValidationAttribute : ValidationAttribute
+{
+    public NejValidationAttribute(string errorMsg = null)
+    {
+        ErrorMessage = errorMsg ?? $"Invalid format";
+    }
+
+    public abstract string ExampleJson { get; }
+
+    public virtual void ApplySchema(OpenApiSchema schema) { }
+}
\ No newline at end of file
diff --git a/Validation/NejValidationAttributeFilter.cs b/Validation/NejValidationAttributeFilter.cs
new file mode 100644
index 0000000..f19bb98
--- /dev/null
+++ b/Validation/NejValidationAttributeFilter.cs
@@ -0,0 +1,42 @@
+using Microsoft.OpenApi.Models;
+using Swashbuckle.AspNetCore.SwaggerGen;
+
+namespace NejCommon.Validation;
+
+public class NejValidationAttributeFilter : ISchemaFilter
+{
+    public void Apply(OpenApiSchema schema, SchemaFilterContext context)
+    {
+        var type = context.Type;
+        var attrOnType = context.MemberInfo?.GetCustomAttributes(typeof(NejValidationAttribute), true)?.Select(a => a as NejValidationAttribute)?.FirstOrDefault();
+        if (attrOnType != null)
+        {
+            Console.WriteLine("Added examples for: " + context.MemberInfo?.Name);
+            schema.Example = OpenApiAnyFactory.CreateFromJson(attrOnType.ExampleJson);
+            attrOnType.ApplySchema(schema);
+        }
+
+        var attrOnType2 = context.ParameterInfo?.GetCustomAttributes(typeof(NejValidationAttribute), true)?.Select(a => a as NejValidationAttribute)?.FirstOrDefault();
+        if (attrOnType2 != null)
+        {
+            Console.WriteLine("Added examples for: " + context.ParameterInfo?.Name);
+            schema.Example = OpenApiAnyFactory.CreateFromJson(attrOnType2.ExampleJson);
+            attrOnType.ApplySchema(schema);
+        }
+
+        foreach (var prop in type.GetProperties())
+        {
+            if (schema.Properties.TryGetValue(prop.Name, out var pschema))
+            {
+                Console.WriteLine("Schema for: " + prop.Name);
+                var attr = prop.GetCustomAttributes(typeof(NejValidationAttribute), true).Select(a => a as NejValidationAttribute).FirstOrDefault();
+                if (attr != null)
+                {
+                    Console.WriteLine("Added examples for: " + prop.Name);
+                    pschema.Example = OpenApiAnyFactory.CreateFromJson(attr.ExampleJson);
+                    attrOnType.ApplySchema(schema);
+                }
+            }
+        }
+    }
+}
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diff --git a/Validation/RegexAttribute.cs b/Validation/RegexAttribute.cs
new file mode 100644
index 0000000..9b75f56
--- /dev/null
+++ b/Validation/RegexAttribute.cs
@@ -0,0 +1,36 @@
+
+using System.ComponentModel.DataAnnotations;
+using System.Text.Json;
+using System.Text.RegularExpressions;
+using Microsoft.OpenApi.Models;
+
+namespace NejCommon.Validation;
+
+public class RegexAttribute : NejValidationAttribute
+{
+    public override string ExampleJson { get; }
+    public string Pattern { get; }
+    public RegexAttribute(string pattern, string example, string errorMsg = null)
+    {
+        Pattern = pattern;
+        ExampleJson = JsonSerializer.Serialize(example);
+        ErrorMessage = errorMsg ?? $"Invalid format (must match {pattern})";
+    }
+
+    protected override ValidationResult IsValid(object value, ValidationContext ctx)
+    {
+        if (value is null)
+            return ValidationResult.Success!;
+        
+        var str = value as string;
+        if (string.IsNullOrWhiteSpace(str) || !Regex.IsMatch(str, Pattern))
+            return new ValidationResult(ErrorMessage);
+        return ValidationResult.Success!;
+    }
+
+    public override void ApplySchema(OpenApiSchema schema)
+    {
+        base.ApplySchema(schema);
+        schema.Pattern = Pattern;
+    }
+}
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