fix: Update TLS protocol and OpenXML installation via NuGet

Install-Dependencies.ps1

@@ -5,7 +5,7 @@ Installs prerequisites for SharePoint XLS Converter application
 #>
 
 # Enable TLS 1.2 for secure connections
-[Net.ServicePointManager]::SecurityProtocol = [Net.ServicePointProtocolType]::Tls12
+[Net.ServicePointManager]::SecurityProtocol = [enum]::Parse([Net.SecurityProtocolType], "Tls12")
 
 Write-Host "Installing required modules..." -ForegroundColor Cyan
 
@@ -32,24 +32,29 @@ foreach ($module in $graphModules) {
     }
 }
 
-# Install DocumentFormat.OpenXml module
-if (-not (Get-Module -ListAvailable -Name DocumentFormat.OpenXml)) {
-    try {
-        # Install NuGet package provider if not exists
-        if (-not (Get-PackageProvider -Name NuGet)) {
-            Install-PackageProvider -Name NuGet -Force
-        }
-        Install-Module DocumentFormat.OpenXml -Scope CurrentUser -Force -AllowClobber
-        Write-Host "DocumentFormat.OpenXml module installed successfully" -ForegroundColor Green
+# Install OpenXML via NuGet package (not module)
+try {
+    # Install NuGet package provider if not exists
+    if (-not (Get-PackageProvider -Name NuGet)) {
+        Install-PackageProvider -Name NuGet -Force
     }
-    catch {
-        Write-Host "Failed to install ${module} module: $($_.Exception.Message)" -ForegroundColor Red
-        Write-Host "You may need to install the Open XML SDK manually." -ForegroundColor Yellow
-        # Do not exit, as the application might still work if the assembly is in the GAC or a known path
+    
+    # Install OpenXML SDK package
+    $openXmlPackage = Install-Package DocumentFormat.OpenXml -Source https://www.nuget.org/api/v2/ -Force -SkipDependencies
+    $dllPath = Join-Path $openXmlPackage.PackageSource "lib\net46\DocumentFormat.OpenXml.dll"
+    
+    if (Test-Path $dllPath) {
+        Add-Type -Path $dllPath
+        Write-Host "DocumentFormat.OpenXml assembly loaded successfully" -ForegroundColor Green
+    }
+    else {
+        throw "OpenXML DLL not found at $dllPath"
     }
 }
-else {
-    Write-Host "DocumentFormat.OpenXml module is already installed" -ForegroundColor Yellow
+catch {
+    Write-Host "Failed to install DocumentFormat.OpenXml: $($_.Exception.Message)" -ForegroundColor Red
+    Write-Host "You may need to install the Open XML SDK manually from:"
+    Write-Host "https://www.microsoft.com/en-us/download/details.aspx?id=30425" -ForegroundColor Yellow
 }
 
 # Check for Excel installation

MainForm.ps1

@@ -2,20 +2,14 @@ Add-Type -AssemblyName System.Windows.Forms
 Import-Module Microsoft.Graph.Sites
 Import-Module Microsoft.Graph.Files
 
-# Load Open XML assembly
+# Load Open XML assembly from installed NuGet package
 try {
-    # Try loading from GAC
-    Add-Type -AssemblyName "DocumentFormat.OpenXml, Version=2.5.5631.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"
+    $openXmlPath = Join-Path $env:USERPROFILE ".nuget\packages\DocumentFormat.OpenXml\*\lib\net46\DocumentFormat.OpenXml.dll"
+    Add-Type -Path (Resolve-Path $openXmlPath -ErrorAction Stop)
 }
 catch {
-    try {
-        # Try loading from a default path
-        Add-Type -Path "C:\Program Files\Microsoft Office\root\Office16\DocumentFormat.OpenXml.dll"
-    }
-    catch {
-        [System.Windows.Forms.MessageBox]::Show("Error loading DocumentFormat.OpenXml.dll. Make sure it is installed and the path is correct.")
-        return
-    }
+    [System.Windows.Forms.MessageBox]::Show("OpenXML assembly missing! Install dependencies first.")
+    exit
 }
 
 # Import our components