using c#: Write an application named TestScores that continuously prompts a user for test scores until the user enters a sentinel value. A valid score ranges from 0 through 100. When the user enters a...

using c#:

Write an application named
TestScores
that continuously prompts a user for test scores until the user enters a sentinel value. A valid score ranges from 0 through 100. When the user enters a valid score, add it to a total; when the user enters an invalid score, display an error message. Before the program ends, display the number of scores entered their average.