Checking a file for integers then outputting a warning C#

Question

So far I have written code to check if a file name exists and outputs an error if no file.

 //does the file exist?
    if (!System.IO.File.Exists(fileName))
    {
       MessageBox.Show("Error: No such file.");
       return;
    }

Now I am suppose to check to see if the file contains integers, and if there are no integers in the file, then I need to output a warning saying that the file does not contain integers. I do not know where to start when it comes to this code. Is there a specific command that just automatically checks for integers?

So far I have written this code to convert the strings to integers from a file (that i created that contains integers)

// convert each string into an integer and store in "eachInt[]"
    string fileContents = System.IO.File.ReadAllText(fileName);
    string[] eachString = fileContents.Split(new char[] { ' ', '\t', '\r', '\n' }, StringSplitOptions.RemoveEmptyEntries);
    int[] eachInt = new int[eachString.Length];
    for (int i = 0; i < eachString.Length; i++)
        eachInt[i] = int.Parse(eachString[i]);

Answer 1

You can use:

if(fileContents.Any(char.IsDigit))

Since you have already read the file contents in a string.

If you don't want to load all the file in memory then you can do

foreach (var line in File.ReadLines("filePath"))
{
    if (line.Any(char.IsDigit))
    {
        //number found. 
        return;//return found etc
    }
}