help me to do use webcam for capture Image

If the camera you are using has a DirectShow driver, you can do that with few lines of code using LEADTOOLS multimedia toolkit:

/*************************************/
Leadtools.Multimedia.CaptureCtrl captureCtrl1;

captureCtrl1 = new Leadtools.Multimedia.CaptureCtrl();

//Select the video devices.
captureCtrl1.VideoDevices[0].Selected = true;
         
//Enable preview.
captureCtrl1.Preview = true;
         
//Set the cpture mode to Still.
captureCtrl1.StartCapture(Leadtools.Multimedia.CaptureMode.Still);
         
//Get the image from capture device.
pictureBox1.Image = captureCtrl1.GetStillImage(500);
/*************************************/

Disclaimer: I work for the company that created this library.