From 0e367abc3d1e563575fe5510e278edc673042fce Mon Sep 17 00:00:00 2001
From: Vladimir Pecanac <vladimir.pecanac@gmail.com>
Date: Sun, 1 Nov 2026 13:29:38 +0100
Subject: [PATCH] Convert string to char: move to .NET 10, add indexer and
 TryParse helpers and tests

---
 ...ConvertingStringToCharArrayInCSharp.csproj |  2 +-
 .../Program.cs                                | 11 +++-
 .../StringHelper.cs                           | 28 +++++++----
 ...rtingStringToCharArrayInCSharpTests.csproj | 10 ++--
 .../StringHelperTests.cs                      | 50 +++++++++++++++++--
 5 files changed, 82 insertions(+), 19 deletions(-)

diff --git a/strings-csharp/ConvertingStringToCharArrayInCSharp/ConvertingStringToCharArrayInCSharp/ConvertingStringToCharArrayInCSharp.csproj b/strings-csharp/ConvertingStringToCharArrayInCSharp/ConvertingStringToCharArrayInCSharp/ConvertingStringToCharArrayInCSharp.csproj
index 2150e3797b..ed9781c223 100644
--- a/strings-csharp/ConvertingStringToCharArrayInCSharp/ConvertingStringToCharArrayInCSharp/ConvertingStringToCharArrayInCSharp.csproj
+++ b/strings-csharp/ConvertingStringToCharArrayInCSharp/ConvertingStringToCharArrayInCSharp/ConvertingStringToCharArrayInCSharp.csproj
@@ -2,7 +2,7 @@
 
   <PropertyGroup>
     <OutputType>Exe</OutputType>
-    <TargetFramework>net8.0</TargetFramework>
+    <TargetFramework>net10.0</TargetFramework>
     <ImplicitUsings>enable</ImplicitUsings>
     <Nullable>enable</Nullable>
   </PropertyGroup>
diff --git a/strings-csharp/ConvertingStringToCharArrayInCSharp/ConvertingStringToCharArrayInCSharp/Program.cs b/strings-csharp/ConvertingStringToCharArrayInCSharp/ConvertingStringToCharArrayInCSharp/Program.cs
index 191cb4da4f..58553e9acf 100644
--- a/strings-csharp/ConvertingStringToCharArrayInCSharp/ConvertingStringToCharArrayInCSharp/Program.cs
+++ b/strings-csharp/ConvertingStringToCharArrayInCSharp/ConvertingStringToCharArrayInCSharp/Program.cs
@@ -8,10 +8,19 @@
 char singleChar = StringHelper.ConvertSingleCharacterStringToChar(singleCharString);
 Console.WriteLine(singleChar);
 
+char firstChar = StringHelper.GetCharacterAtIndex(myString, 0);
+char lastChar = myString[^1];
+Console.WriteLine($"{firstChar} {lastChar}");
+
+if (StringHelper.TryConvertSingleCharacterStringToChar("AB", out char parsed))
+    Console.WriteLine(parsed);
+else
+    Console.WriteLine("Not a single character");
+
 ReadOnlySpan<char> charArrayReadOnlySpan = StringHelper.ConvertStringToCharArrayUsingReadOnlySpan(myString);
 PrintArray(charArrayReadOnlySpan);
 
-string[] stringArray = { "C#", "is", "awesome" };
+string[] stringArray = ["C#", "is", "awesome"];
 char[] combinedCharArray = StringHelper.ConvertStringArrayToCharArrayUsingLoop(stringArray);
 PrintArray(combinedCharArray);
 
diff --git a/strings-csharp/ConvertingStringToCharArrayInCSharp/ConvertingStringToCharArrayInCSharp/StringHelper.cs b/strings-csharp/ConvertingStringToCharArrayInCSharp/ConvertingStringToCharArrayInCSharp/StringHelper.cs
index 57f2a62f03..294ce303c5 100644
--- a/strings-csharp/ConvertingStringToCharArrayInCSharp/ConvertingStringToCharArrayInCSharp/StringHelper.cs
+++ b/strings-csharp/ConvertingStringToCharArrayInCSharp/ConvertingStringToCharArrayInCSharp/StringHelper.cs
@@ -19,20 +19,30 @@ public static char ConvertSingleCharacterStringToChar(string inputString)
         return char.Parse(inputString);
     }
 
-public static char[] ConvertStringArrayToCharArrayUsingLoop(string[] stringArray)
-{
-    var combinedString = new StringBuilder();
+    public static char GetCharacterAtIndex(string inputString, int index)
+    {
+        return inputString[index];
+    }
 
-    foreach (var str in stringArray)
+    public static bool TryConvertSingleCharacterStringToChar(string? inputString, out char result)
     {
-        combinedString.Append(str);
+        return char.TryParse(inputString, out result);
     }
 
-    var result = new char[combinedString.Length];
-    combinedString.CopyTo(0, result, 0, result.Length);
+    public static char[] ConvertStringArrayToCharArrayUsingLoop(string[] stringArray)
+    {
+        var combinedString = new StringBuilder();
 
-    return result;
-}
+        foreach (var str in stringArray)
+        {
+            combinedString.Append(str);
+        }
+
+        var result = new char[combinedString.Length];
+        combinedString.CopyTo(0, result, 0, result.Length);
+
+        return result;
+    }
 
     public static char[] ConvertStringArrayToCharArrayUsingLinq(string[] stringArray)
     {
diff --git a/strings-csharp/ConvertingStringToCharArrayInCSharp/ConvertingStringToCharArrayInCSharpTests/ConvertingStringToCharArrayInCSharpTests.csproj b/strings-csharp/ConvertingStringToCharArrayInCSharp/ConvertingStringToCharArrayInCSharpTests/ConvertingStringToCharArrayInCSharpTests.csproj
index b93b3680e1..1f585b4a46 100644
--- a/strings-csharp/ConvertingStringToCharArrayInCSharp/ConvertingStringToCharArrayInCSharpTests/ConvertingStringToCharArrayInCSharpTests.csproj
+++ b/strings-csharp/ConvertingStringToCharArrayInCSharp/ConvertingStringToCharArrayInCSharpTests/ConvertingStringToCharArrayInCSharpTests.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>net8.0</TargetFramework>
+    <TargetFramework>net10.0</TargetFramework>
     <ImplicitUsings>enable</ImplicitUsings>
     <Nullable>enable</Nullable>
 
@@ -10,13 +10,13 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.3.2" />
-    <PackageReference Include="xunit" Version="2.4.2" />
-    <PackageReference Include="xunit.runner.visualstudio" Version="2.4.5">
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="18.11.0" />
+    <PackageReference Include="xunit" Version="2.9.3" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="4.0.1">
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
       <PrivateAssets>all</PrivateAssets>
     </PackageReference>
-    <PackageReference Include="coverlet.collector" Version="3.1.2">
+    <PackageReference Include="coverlet.collector" Version="10.1.0">
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
       <PrivateAssets>all</PrivateAssets>
     </PackageReference>
diff --git a/strings-csharp/ConvertingStringToCharArrayInCSharp/ConvertingStringToCharArrayInCSharpTests/StringHelperTests.cs b/strings-csharp/ConvertingStringToCharArrayInCSharp/ConvertingStringToCharArrayInCSharpTests/StringHelperTests.cs
index e8fe3ac95f..93cb888237 100644
--- a/strings-csharp/ConvertingStringToCharArrayInCSharp/ConvertingStringToCharArrayInCSharpTests/StringHelperTests.cs
+++ b/strings-csharp/ConvertingStringToCharArrayInCSharp/ConvertingStringToCharArrayInCSharpTests/StringHelperTests.cs
@@ -42,11 +42,55 @@ public void GivenStringArrayToCharArray_WhenValidInput_ThenReturnsCharArray()
         Assert.Equal(InputString.ToCharArray(), resultLinq);
     }
 
+    [Theory]
+    [InlineData("AB")]
+    [InlineData("")]
+    public void GivenStringToChar_WhenLengthIsNotOne_ThenThrowsFormatException(string inputString)
+    {
+        Assert.Throws<FormatException>(() => StringHelper.ConvertSingleCharacterStringToChar(inputString));
+    }
+
     [Fact]
-    public void GivenStringToChar_WhenInvalidInput_ThenThrowsArgumentException()
+    public void GivenStringToChar_WhenNull_ThenThrowsArgumentNullException()
     {
-        const string inputString = "AB";
+        Assert.Throws<ArgumentNullException>(() => StringHelper.ConvertSingleCharacterStringToChar(null!));
+    }
 
-        Assert.Throws<FormatException>(() => StringHelper.ConvertSingleCharacterStringToChar(inputString));
+    [Fact]
+    public void GivenCharacterAtIndex_WhenIndexInRange_ThenReturnsThatChar()
+    {
+        Assert.Equal('H', StringHelper.GetCharacterAtIndex(InputString, 0));
+        Assert.Equal('W', StringHelper.GetCharacterAtIndex(InputString, 7));
+    }
+
+    [Fact]
+    public void GivenCharacterAtIndex_WhenStringIsEmpty_ThenThrowsIndexOutOfRangeException()
+    {
+        Assert.Throws<IndexOutOfRangeException>(() => StringHelper.GetCharacterAtIndex(string.Empty, 0));
+    }
+
+    [Theory]
+    [InlineData("A", true)]
+    [InlineData("AB", false)]
+    [InlineData("", false)]
+    [InlineData(null, false)]
+    public void GivenTryConvert_WhenCalled_ThenReportsSuccessWithoutThrowing(string? inputString, bool expectedSuccess)
+    {
+        bool success = StringHelper.TryConvertSingleCharacterStringToChar(inputString, out char result);
+
+        Assert.Equal(expectedSuccess, success);
+        if (success)
+            Assert.Equal(inputString![0], result);
+    }
+
+    [Fact]
+    public void GivenEmoji_WhenConverted_ThenTwoCharsAndParseFails()
+    {
+        const string thumbsUp = "\U0001F44D";
+
+        Assert.Equal(2, thumbsUp.Length);
+        Assert.True(char.IsHighSurrogate(StringHelper.GetCharacterAtIndex(thumbsUp, 0)));
+        Assert.False(StringHelper.TryConvertSingleCharacterStringToChar(thumbsUp, out _));
+        Assert.Equal(0x1F44D, System.Text.Rune.GetRuneAt(thumbsUp, 0).Value);
     }
 }
\ No newline at end of file