Drop net7.0 target

.NET 7 is EOL since May. The only .NET 7 features we use are
`ObjectDisposedException.ThrowIf` (moved to a throw helper) and
some newer regex features.

This feels a bit weird, but I suppose it is the expected course of action.

Author: Rob-Hague

src/Renci.SshNet/BaseClient.cs

@@ -448,17 +448,10 @@ protected virtual void Dispose(bool disposing)
         /// <summary>
         /// Check if the current instance is disposed.
         /// </summary>
-        /// <exception cref="ObjectDisposedException">THe current instance is disposed.</exception>
+        /// <exception cref="ObjectDisposedException">The current instance is disposed.</exception>
         protected void CheckDisposed()
         {
-#if NET7_0_OR_GREATER
-            ObjectDisposedException.ThrowIf(_isDisposed, this);
-#else
-            if (_isDisposed)
-            {
-                throw new ObjectDisposedException(GetType().FullName);
-            }
-#endif // NET7_0_OR_GREATER
+            ThrowHelper.ThrowObjectDisposedIf(_isDisposed, this);
         }
 
         /// <summary>

src/Renci.SshNet/Common/ChannelInputStream.cs

@@ -116,10 +116,7 @@ public override void Write(byte[] buffer, int offset, int count)
                 throw new ArgumentOutOfRangeException(nameof(offset), "offset or count is negative.");
             }
 
-            if (_isDisposed)
-            {
-                throw CreateObjectDisposedException();
-            }
+            ThrowHelper.ThrowObjectDisposedIf(_isDisposed, this);
 
             if (count == 0)
             {
@@ -208,10 +205,5 @@ public override long Position
             get { return _totalPosition; }
             set { throw new NotSupportedException(); }
         }
-
-        private ObjectDisposedException CreateObjectDisposedException()
-        {
-            return new ObjectDisposedException(GetType().FullName);
-        }
     }
 }

src/Renci.SshNet/Common/PipeStream.cs

@@ -90,7 +90,7 @@ public override void Write(byte[] buffer, int offset, int count)
         {
             lock (_sync)
             {
-                ThrowIfDisposed();
+                ThrowHelper.ThrowObjectDisposedIf(_disposed, this);
 
                 AssertValid();
 
@@ -232,17 +232,5 @@ public override long Position
             get { return 0; }
             set { throw new NotSupportedException(); }
         }
-
-        private void ThrowIfDisposed()
-        {
-#if NET7_0_OR_GREATER
-            ObjectDisposedException.ThrowIf(_disposed, this);
-#else
-            if (_disposed)
-            {
-                throw new ObjectDisposedException(GetType().FullName);
-            }
-#endif // NET7_0_OR_GREATER
-        }
     }
 }

src/Renci.SshNet/Common/ThrowHelper.cs

@@ -0,0 +1,25 @@
+#nullable enable
+using System;
+
+namespace Renci.SshNet.Common
+{
+    internal static class ThrowHelper
+    {
+        public static void ThrowObjectDisposedIf(bool condition, object instance)
+        {
+#if NET7_0_OR_GREATER
+            ObjectDisposedException.ThrowIf(condition, instance);
+#else
+            if (condition)
+            {
+                Throw(instance);
+
+                static void Throw(object? instance)
+                {
+                    throw new ObjectDisposedException(instance?.GetType().FullName);
+                }
+            }
+#endif
+        }
+    }
+}

src/Renci.SshNet/ForwardedPortDynamic.cs

@@ -128,14 +128,7 @@ protected override void StopPort(TimeSpan timeout)
         /// <exception cref="ObjectDisposedException">The current instance is disposed.</exception>
         protected override void CheckDisposed()
         {
-#if NET7_0_OR_GREATER
-            ObjectDisposedException.ThrowIf(_isDisposed, this);
-#else
-            if (_isDisposed)
-            {
-                throw new ObjectDisposedException(GetType().FullName);
-            }
-#endif // NET7_0_OR_GREATER
+            ThrowHelper.ThrowObjectDisposedIf(_isDisposed, this);
         }
 
         /// <summary>

src/Renci.SshNet/ForwardedPortLocal.cs

@@ -164,14 +164,7 @@ protected override void StopPort(TimeSpan timeout)
         /// <exception cref="ObjectDisposedException">The current instance is disposed.</exception>
         protected override void CheckDisposed()
         {
-#if NET7_0_OR_GREATER
-            ObjectDisposedException.ThrowIf(_isDisposed, this);
-#else
-            if (_isDisposed)
-            {
-                throw new ObjectDisposedException(GetType().FullName);
-            }
-#endif // NET7_0_OR_GREATER
+            ThrowHelper.ThrowObjectDisposedIf(_isDisposed, this);
         }
 
         /// <summary>

src/Renci.SshNet/ForwardedPortRemote.cs

@@ -228,14 +228,7 @@ protected override void StopPort(TimeSpan timeout)
         /// <exception cref="ObjectDisposedException">The current instance is disposed.</exception>
         protected override void CheckDisposed()
         {
-#if NET7_0_OR_GREATER
-            ObjectDisposedException.ThrowIf(_isDisposed, this);
-#else
-            if (_isDisposed)
-            {
-                throw new ObjectDisposedException(GetType().FullName);
-            }
-#endif // NET7_0_OR_GREATER
+            ThrowHelper.ThrowObjectDisposedIf(_isDisposed, this);
         }
 
         private void Session_ChannelOpening(object sender, MessageEventArgs<ChannelOpenMessage> e)

src/Renci.SshNet/Renci.SshNet.csproj

@@ -4,7 +4,7 @@
     <AssemblyName>Renci.SshNet</AssemblyName>
     <Product>SSH.NET</Product>
     <AssemblyTitle>SSH.NET</AssemblyTitle>
-    <TargetFrameworks>net462;netstandard2.0;netstandard2.1;net6.0;net7.0;net8.0</TargetFrameworks>
+    <TargetFrameworks>net462;netstandard2.0;netstandard2.1;net6.0;net8.0</TargetFrameworks>
   </PropertyGroup>
 
   <PropertyGroup>

src/Renci.SshNet/Sftp/SftpFileReader.cs

@@ -74,14 +74,7 @@ public SftpFileReader(byte[] handle, ISftpSession sftpSession, uint chunkSize, i
 
         public byte[] Read()
         {
-#if NET7_0_OR_GREATER
-            ObjectDisposedException.ThrowIf(_disposingOrDisposed, this);
-#else
-            if (_disposingOrDisposed)
-            {
-                throw new ObjectDisposedException(GetType().FullName);
-            }
-#endif // NET7_0_OR_GREATER
+            ThrowHelper.ThrowObjectDisposedIf(_disposingOrDisposed, this);
 
             if (_exception is not null)
             {

src/Renci.SshNet/Sftp/SftpFileStream.cs

@@ -1364,14 +1364,7 @@ private void SetupWrite()
 
         private void CheckSessionIsOpen()
         {
-#if NET7_0_OR_GREATER
-            ObjectDisposedException.ThrowIf(_session is null, this);
-#else
-            if (_session is null)
-            {
-                throw new ObjectDisposedException(GetType().FullName);
-            }
-#endif // NET7_0_OR_GREATER
+            ThrowHelper.ThrowObjectDisposedIf(_session is null, this);
 
             if (!_session.IsOpen)
             {