exception meaning in .net core
//Using the snippet shown above, the error page will show the offending line in red, with a variable number of lines of code above it. The number of lines is determined by the value of SourceCodeLineCount, which is set to 2 in this case.
var options = new DeveloperExceptionPageOptions
{
SourceCodeLineCount = 2
};
app.UseDeveloperExceptionPage(options);