Attributing text rating to a numerical average

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C#

Microsoft

I have a project at school that I'm struggling with. We use the Microsoft Visual Studio to build Windows Forms using .NET framework. I have my form functional for calculating the numerical average and having that output to the label I've set for that.

My issue is I have formatted nested if loops that tell it if the average is 95 or higher then the restaurant is rated as "Four Star". There are 5 of these text ratings. My issue is I have no clue how to code the output and have it display in the label I've set for that purpose. I'll include a screenshot of my program.

I played around with my variable "rate" to attempt to create code that is agreeable in Microsoft Visual Studio. I hope this is all comprehensible and that you know what I'm asking. When the program is run it shows an error "An unhandled exception of type 'System.FormatException' occurred in mscorlib.dll Additional information: Input string was not in a correct format." This error shows applying to the "rate" variable.

I honestly am brand new to C# and have realized there is a lot of differences between this and C as well as this IDE and the IDE I was using before. Thank you in advance.

***NOTE*** I am not looking for someone to do the work for me. But maybe help guide me and help me understand why it is the way it is.

What I have tried:

int hours = short.Parse(txtHours.Text);
           int menu = short.Parse(txtMenu.Text);
           int friend = short.Parse(txtFriendliness.Text);
           int prices = short.Parse(txtPrices.Text);
           int clean = short.Parse(txtCleanliness.Text);
           int total = hours + menu + friend + prices + clean + clean;
           float rate = float.Parse(lblRating.Text);
           float rating = (float)total / 6;


           //Processing
           if (rating >= 95)
           {
              Console.WriteLine(rate.ToString("Four Star"));
           }else if (rating >= 85)
           {
               Console.WriteLine(rate.ToString("Fine Dining"));
           }else if (rating >= 75)
           {
               Console.WriteLine(rate.ToString("Good"));
           }else if (rating >= 65)
           {
               Console.WriteLine(rate.ToString("Okay"));
           }else
           {
               Console.WriteLine(rate.ToString("Poor"));
           }

           //Output
           lblAverage.Text = rating.ToString("n0");
           lblRating.Text = rate.ToString("a");