DirectX about the view matrix

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C++

DirectX

Problem:
I get a problem with the exercise in the 《Introduction To 3D Game Programming with DirectX 9.0, A shade Approach》. In the chapter 7 ,exercise 1 .
I want to draw polyline with the DrawPrimitive() method . Here is my code about the vertex buffer :

void Exercise::buildVB()
{
    //get Direct3D Device
    IDirect3DDevice9* _pDevice = m_pD3d->getDevice();

    //craete the vertex buffer
    HR(_pDevice->CreateVertexBuffer(6 * sizeof(VertexPos),D3DUSAGE_WRITEONLY,0,
        D3DPOOL_MANAGED,&m_pVB,0));

    //lock the vertex buffer
    VertexPos * _pData = NULL ;
    HR(m_pVB->Lock(0,0,(void**)&_pData,0));

    //set the vertex
    /*_pData[0] = VertexPos(0.0f, 0.0f, 0.0f);
    _pData[1] = VertexPos(1.0f, 0.0f, -3.0f);
    _pData[2] = VertexPos(3.0f, 0.0f, -2.0f);
    _pData[3] = VertexPos(2.0f, 0.0f, -1.0f);
    _pData[4] = VertexPos(2.5f, 0.0f, 1.0f);
    _pData[5] = VertexPos(1.0f, 0.0f, 3.0f);*/
    _pData[0] = VertexPos(0.0f, 0.0f, 0.0f);
    _pData[1] = VertexPos(0.1f, -0.3f,0.0f );
    _pData[2] = VertexPos(0.3f, -0.2f, 0.0f);
    _pData[3] = VertexPos(0.2f, -0.1f,0.0f );
    _pData[4] = VertexPos(0.25f, 0.1f,0.0f );
    _pData[5] = VertexPos(0.1f, 0.3f,0.0f );


    //unlock the vertex buffer
    HR(m_pVB->Unlock());
}

When I draw the image with the following method , it is OK . The image will display . Here is my code :

void Exercise::draw()
{
    //get Direct3D Device
    IDirect3DDevice9* _pDevice = m_pD3d->getDevice();

    //set stream source
    HR(_pDevice->SetStreamSource(0,m_pVB,0,sizeof(VertexPos)));

    //set the index
    //HR(_pDevice->SetIndices(m_pIB));

    //set the vertex declaration
    HR(_pDevice->SetVertexDeclaration(VertexPos::_vertexDecl));

    //set the world matrix
    //D3DXMATRIX _worldM ;
    //HR(_pDevice->SetTransform(D3DTS_WORLD,D3DXMatrixIdentity(&_worldM)));

    //set the view matrix
    //HR(_pDevice->SetTransform(D3DTS_VIEW,&m_ViewM));

    //set the projection matrix
    //HR(_pDevice->SetTransform(D3DTS_PROJECTION,&m_ProjM));

    //set the render state
    HR(_pDevice->SetRenderState(D3DRS_FILLMODE,D3DFILL_WIREFRAME));

    //draw the primitive
    HR(_pDevice->DrawPrimitive(D3DPT_LINESTRIP,0,6));

}

But , when I draw the image with the following code , I can not see image in screen .

void Exercise::draw()
{
	//get Direct3D Device
	IDirect3DDevice9* _pDevice = m_pD3d->getDevice();

	//set stream source
	HR(_pDevice->SetStreamSource(0,m_pVB,0,sizeof(VertexPos)));

	//set the index
	//HR(_pDevice->SetIndices(m_pIB));

	//set the vertex declaration
	HR(_pDevice->SetVertexDeclaration(VertexPos::_vertexDecl));

	//set the world matrix
	D3DXMATRIX _worldM ;
	HR(_pDevice->SetTransform(D3DTS_WORLD,D3DXMatrixIdentity(&_worldM)));

	//set the view matrix
	HR(_pDevice->SetTransform(D3DTS_VIEW,&m_ViewM));

	//set the projection matrix
	HR(_pDevice->SetTransform(D3DTS_PROJECTION,&m_ProjM));

	//set the render state
	HR(_pDevice->SetRenderState(D3DRS_FILLMODE,D3DFILL_WIREFRAME));

	//draw the primitive
	HR(_pDevice->DrawPrimitive(D3DPT_LINESTRIP,0,6));
	
}

The view matrix and projection matrix is here :

void Exercise::buildViewM()
{
	D3DXVECTOR3 _pos(0.0f,0.0f,-10);
	D3DXVECTOR3 _target(0.0f,0.0f,0.0f);
	D3DXVECTOR3 _up(0.0f,1.0f,0.0f);
	D3DXMatrixLookAtLH(&m_ViewM,&_pos,&_target,&_up);
}

void Exercise::buildProjM()
{
	float _width = m_pD3d->getD3dParam().BackBufferWidth;
	float _height = m_pD3d->getD3dParam().BackBufferHeight;
	D3DXMatrixPerspectiveFovLH(&m_ProjM,D3DX_PI,_width/_height,1.0f,1000.0f);
}

I draw a image in x-y plane , and then put the eye in the (0.0f,0.0f,-10.0f) . I do not understand why I can not see the image .

Is there anyone who can help me ?