[c#] Fix Table __vector_as_array correct len calc (#8911)

* fix for https://github.com/google/flatbuffers/issues/8759
__vector_as_array<T> calling ByteBuffer.ToArray<T> with the length in bytes by multiplying len with ByteBuffer.Sizeof<T> and FlatBuffersExampleTests extended to call GetVectorOfLongsArray/GetVectorOfDoublesArray which failed without the fix

* first try to repair build-dotnet-windows

* syntax error fixed

* Update solution creation command in build workflow

add --format sln to the dotnet new command, maybe it is currently creating a .slnx instead?

.github/workflows/build.yml

diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 3ca3f11..30e0cec 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -197,8 +197,7 @@
         configuration: [
           '',
           '-p:UnsafeByteBuffer=true',
-          # Fails two tests currently.
-          #'-p:EnableSpanT=true,UnsafeByteBuffer=true'
+          '-p:EnableSpanT=true,UnsafeByteBuffer=true'
           ]
     steps:
     - uses: actions/checkout@v6
@@ -209,7 +208,7 @@
     - name: Build
       run: |
         cd tests\FlatBuffers.Test
-        dotnet new sln --force --name FlatBuffers.Test
+        dotnet new sln --force --name FlatBuffers.Test --format sln
         dotnet sln FlatBuffers.Test.sln add FlatBuffers.Test.csproj
         dotnet build -c Release ${{matrix.configuration}} FlatBuffers.Test.sln
     - name: Run net6.0

net/FlatBuffers/Table.cs

diff --git a/net/FlatBuffers/Table.cs b/net/FlatBuffers/Table.cs
index d6d9d09..5dde28e 100644
--- a/net/FlatBuffers/Table.cs
+++ b/net/FlatBuffers/Table.cs
@@ -150,7 +150,7 @@
 
             var pos = this.__vector(o);
             var len = this.__vector_len(o);
-            return bb.ToArray<T>(pos, len);
+            return bb.ToArray<T>(pos, len * ByteBuffer.SizeOf<T>());
         }
 
         // Initialize any Table-derived type to point to the union at the given offset.

tests/FlatBuffers.Test/FlatBuffersExampleTests.cs

diff --git a/tests/FlatBuffers.Test/FlatBuffersExampleTests.cs b/tests/FlatBuffers.Test/FlatBuffersExampleTests.cs
index dc541be..d577457 100644
--- a/tests/FlatBuffers.Test/FlatBuffersExampleTests.cs
+++ b/tests/FlatBuffers.Test/FlatBuffersExampleTests.cs
@@ -1,4 +1,4 @@
-/*
+/*
  * Copyright 2014 Google Inc. All rights reserved.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
@@ -90,6 +90,9 @@
             fbb.AddOffset(test1.Value);
             var testArrayOfString = fbb.EndVector();
 
+            var longsVector = Monster.CreateVectorOfLongsVector(fbb, new long[] { 1, 100, 10000, 1000000, 100000000 });
+            var doublesVector = Monster.CreateVectorOfDoublesVector(fbb, new double[] { -1.7976931348623157e+308, 0, 1.7976931348623157e+308 });
+
             Monster.StartMonster(fbb);
             Monster.AddPos(fbb, Vec3.CreateVec3(fbb, 1.0f, 2.0f, 3.0f, 3.0,
                                                      Color.Green, (short)5, (sbyte)6));
@@ -102,6 +105,8 @@
             Monster.AddTestarrayofstring(fbb, testArrayOfString);
             Monster.AddTestbool(fbb, true);
             Monster.AddTestarrayoftables(fbb, sortMons);
+            Monster.AddVectorOfLongs(fbb, longsVector);
+            Monster.AddVectorOfDoubles(fbb, doublesVector);
             var mon = Monster.EndMonster(fbb);
 
             if (sizePrefix)
@@ -285,6 +290,13 @@
                 Assert.IsTrue(monster.GetTestarrayofboolsBytes().HasValue);
             }
             #endif
+
+            var longArray = monster.GetVectorOfLongsArray();
+            Assert.AreEqual(5, longArray.Length);
+            Assert.AreEqual(100, longArray[1]);
+
+            var doublesArray = monster.GetVectorOfDoublesArray();
+            Assert.AreEqual(3, doublesArray.Length);
         }
 
         [FlatBuffersTestMethod]