[a-zA-Z]

[\u0600-\u06FF]
[ا-یءئ]

using System.Text.RegularExpressions;

namespace sample
{
   public static class CDetectFarsi
   {
       public static bool ContainsFarsiData(this string txt)
       {
           return !string.IsNullOrEmpty(txt) &&
                   Regex.IsMatch(txt, "[ا-یءئ]");
       }

       public static bool ContainsFarsi(this string txt)
       {
           return !string.IsNullOrEmpty(txt) &&
                   Regex.IsMatch(txt, @"[\u0600-\u06FF]");
       }
   }
}

using NUnit.Framework;
using sample;

namespace TestLibrary
{
   [TestFixture]
   public class TestFarsiClass
   {
       /*******************************************************************************/
       [Test]
       public void TestContainsFarsi1()
       {
           Assert.IsTrue("وحید".ContainsFarsi());
       }

       [Test]
       public void TestContainsFarsi2()
       {
           Assert.IsTrue("گردان".ContainsFarsi());
       }

       [Test]
       public void TestContainsFarsi3()
       {
           Assert.IsTrue("سپیدTest".ContainsFarsi());
       }

       [Test]
       public void TestContainsFarsi4()
       {
           Assert.IsTrue("123بررسی456".ContainsFarsi());
       }

       [Test]
       public void TestContainsFarsi5()
       {
           Assert.IsFalse("Book".ContainsFarsi());
       }

       [Test]
       public void TestContainsFarsi6()
       {
           Assert.IsTrue("۱۳۸۷".ContainsFarsi());
       }

       [Test]
       public void TestContainsFarsi7()
       {
           Assert.IsFalse("Здравствуйте!".ContainsFarsi()); //Russian hello!
       }

      
       /*******************************************************************************/
       [Test]
       public void TestContainsFarsiData1()
       {
           Assert.IsTrue("وحید".ContainsFarsiData());
       }

       [Test]
       public void TestContainsFarsiData2()
       {
           Assert.IsTrue("گردان".ContainsFarsiData());
       }

       [Test]
       public void TestContainsFarsiData3()
       {
           Assert.IsTrue("سپیدTest".ContainsFarsiData());
       }

       [Test]
       public void TestContainsFarsiData4()
       {
           Assert.IsTrue("123بررسی456".ContainsFarsiData());
       }

       [Test]
       public void TestContainsFarsiData5()
       {
           Assert.IsFalse("Book".ContainsFarsiData());
       }

       [Test]
       public void TestContainsFarsiData6()
       {
           Assert.IsTrue("۱۳۸۷".ContainsFarsiData());
       }

       [Test]
       public void TestContainsFarsiData7()
       {
           Assert.IsFalse("Здравствуйте!".ContainsFarsiData()); //Russian hello!
       }
   }
}

[Test,Ignore]

Test[MethodToBeTested][SomeAttribute]