There are two ways to access Mat Image's pixel value in EmguCV (C#).
1- Convert Mat Image to Image<ColorType, DDepth>
2- Use Image.Data.GetValue() Functions
1- you can convert your Mat image to Image Format and then access the pixel values just like below:
int row = 0;
int col = 5;
int Channel = 0;
Mat ImageMat = CvInvoke.Imread("Image/Path");
Image<Gray, Byte> ImageFormat = ImageMat.ToImage<Gray, Byte>();
int pixel_value = ImageFormat.Data[row, col, Channel];
2- you can directly access pixel value.GetValue method for Mat Class.
but this method returns an object you have to convert to a datatype like an int to float eg.
Mat ImageMat = CvInvoke.Imread("Image/Path");
object pixel_value = ImageMat.Data.GetValue(row, col, Channel);
float pixelVal = Convert.ToInt32(pixel_value);