Rahmen von TextBox anpassen

[martin_pavel]

Hi,

ich möchte dem TextBox-Rahmen eine andere Farbe geben (zum Beispiel rot).
Durch die Ableitung von der TextBox Klasse und Beobachtung des WM_NCPAINT Messages habe ich eine Lösung gebastelt, die aber ein kleines Problemchen mit dem Clientbereich hat:
wenn das Control upgedated wird, entstehen im Clientbereich am Rahmen zufällige Punkte.

So sieht das aus:

#pragma once

namespace TestTextBox
{
	using namespace System;
	using namespace System::ComponentModel;
	using namespace System::Collections;
	using namespace System::Windows::Forms;
	using namespace System::Data;
	using namespace System::Drawing;
	using namespace System::Windows::Forms::VisualStyles;
	using namespace System::Runtime::InteropServices;

	/// <summary>Die Klasse unterdrückt die Bearbeitung der Evens Keys::Tab und Keys::Enter</summary>
	public ref class MyTextBox : public System::Windows::Forms::TextBox
	{

	 public: 
       [DllImport("USER32.DLL")] 
       static IntPtr GetWindowDC(IntPtr hWND); 

       [DllImport("USER32.DLL")] 
       static int ReleaseDC(IntPtr hWND, IntPtr hDC);

       [DllImport("USER32.DLL")] 
       static IntPtr GetDCEx (IntPtr hWND, IntPtr hrgnClip, int flags);

       [DllImport("GDI32.DLL")] 
       static IntPtr CreateRectRgn (int nLeftRect, int nTopRect, int nRightRect, int nBottomRect);

   private:
      static const Int32 WM_NCPAINT = 0x0085;
	  static const Int32 WM_NCCALCSIZE = 0x0083;

	public: MyTextBox()
			{
				__super::TextBox();
				m_ErrorFlag = false;
			}

	//[SecurityPermission(SecurityAction::Demand, Flags=SecurityPermissionFlag::UnmanagedCode)]
    virtual void WndProc (Message% m) override
      {
         switch ( m.Msg )
         {
            case WM_NCPAINT:

				if (DrawNCBorder (m))
					return;
				break;

			case WM_NCCALCSIZE:
				break;

         }

         TextBox::WndProc( m );
      }

	private: 
	bool DrawNCBorder(Message% m) 
	{
		IntPtr hDC = GetWindowDC (m.HWnd);

		if (hDC.ToInt32() == 0)
			return false;

		Graphics^ gr = Graphics::FromHdc (hDC); 
		if (gr != nullptr)
		{
			Rectangle bounds(0, 0, this->Size.Width , this->Size.Height);
			ControlPaint::DrawBorder (gr, bounds, Color::Red, ButtonBorderStyle::Solid);

			m.Result = (IntPtr)1; 
			ReleaseDC (m.HWnd, hDC);

			return true;
	    }
		else
		{
			return false;
		}

	}

	public:
		bool m_ErrorFlag;

	};

	public ref class Form1 : public System::Windows::Forms::Form
	{
	public:
		Form1(void)
		{
			InitializeComponent();
			//
			//TODO: Add the constructor code here
			//

		}

	protected:
		/// <summary>
		/// Clean up any resources being used.
		/// </summary>
		~Form1()
		{
			if (components)
			{
				delete components;
			}
		}
	private: MyTextBox^  textBox1;
	private: System::Windows::Forms::Button^  button1;

	protected: 

	private:
		/// <summary>
		/// Required designer variable.
		/// </summary>
		System::ComponentModel::Container ^components;

#pragma region Windows Form Designer generated code
		/// <summary>
		/// Required method for Designer support - do not modify
		/// the contents of this method with the code editor.
		/// </summary>
		void InitializeComponent(void)
		{
			this->textBox1 = (gcnew MyTextBox());
			this->button1 = (gcnew System::Windows::Forms::Button());
			this->SuspendLayout();
			// 
			// textBox1
			// 
			this->textBox1->Location = System::Drawing::Point(33, 58);
			this->textBox1->Multiline = true;
			this->textBox1->Name = L"textBox1";
			this->textBox1->Size = System::Drawing::Size(100, 40);
			this->textBox1->TabIndex = 0;
			this->textBox1->RightToLeft = System::Windows::Forms::RightToLeft::Yes;
			// button1
			// 
			this->button1->Location = System::Drawing::Point(22, 141);
			this->button1->Name = L"button1";
			this->button1->Size = System::Drawing::Size(75, 23);
			this->button1->TabIndex = 1;
			this->button1->Text = L"button1";
			this->button1->UseVisualStyleBackColor = true;
			// 
			// Form1
			// 
			this->AutoScaleDimensions = System::Drawing::SizeF(6, 13);
			this->AutoScaleMode = System::Windows::Forms::AutoScaleMode::Font;
			this->ClientSize = System::Drawing::Size(292, 266);
			this->Controls->Add(this->button1);
			this->Controls->Add(this->textBox1);
			this->Name = L"Form1";
			this->Text = L"Form1";
			this->ResumeLayout(false);
			this->PerformLayout();

		}
#pragma endregion
	};
}

Was fehlt der Lösung?