Fixed imports

samples/ControlCatalog/Pages/OpenGlPage.xaml.cs

@@ -243,9 +243,8 @@ namespace ControlCatalog.Pages
             GL.UseProgram(0);
 
             // Delete all resources.
-            GL.DeleteBuffer(_vertexBufferObject);
-            GL.DeleteBuffer(_indexBufferObject);
-            GL.DeleteVertexArray(_vertexArrayObject);
+            GL.DeleteBuffers(2, new[] { _vertexBufferObject, _indexBufferObject });
+            GL.DeleteVertexArrays(1, new[] { _vertexArrayObject });
             GL.DeleteProgram(_shaderProgram);
             GL.DeleteShader(_fragmentShader);
             GL.DeleteShader(_vertexShader);

src/Avalonia.OpenGL/GlEntryPointAttribute.cs

@@ -6,7 +6,7 @@ namespace Avalonia.OpenGL
     public class GlEntryPointAttribute : Attribute
     {
         public string[] EntryPoints { get; }
-        public bool Optional { get; }
+        public bool Optional { get; set; }
 
         public GlEntryPointAttribute(string entryPoint, bool optional = false)
         {

src/Avalonia.OpenGL/GlInterface.cs

@@ -320,13 +320,13 @@ namespace Avalonia.OpenGL
         [GlEntryPoint("glEnable")]
         public GlEnable Enable { get; }
 
-        public delegate void GlDeleteBuffer(int buffer);
-        [GlEntryPoint("glDeleteBuffer")]
-        public GlDeleteBuffer DeleteBuffer { get; }
+        public delegate void GlDeleteBuffers(int count, int[] buffers);
+        [GlEntryPoint("glDeleteBuffers")]
+        public GlDeleteBuffers DeleteBuffers { get; }
 
-        public delegate void GlDeleteVertexArray(int array);
-        [GlEntryPoint("glDeleteVertexArray", "glDeleteVertexArrayOES")]
-        public GlDeleteVertexArray DeleteVertexArray { get; }
+        public delegate void GlDeleteVertexArrays(int count, int[] buffers);
+        [GlEntryPoint("glDeleteVertexArrays", "glDeleteVertexArraysOES")]
+        public GlDeleteVertexArrays DeleteVertexArrays { get; }
 
         public delegate void GlDeleteProgram(int program);
         [GlEntryPoint("glDeleteProgram")]