The vertex stream and index data of the graphics device must be set before any call to DrawIndexedPrimitives. The following example sets the index data; it associates a user-created vertex buffer of type VertexPositionNormalTexture with vertex stream 0 (zero) of the graphics device.
// Initialize the vertex buffer, allocating memory for each vertex.
vertexBuffer = new VertexBuffer(graphics.GraphicsDevice, vertexDeclaration,
// Set the vertex buffer data to the array of vertices.