Operator '>=' cannot be applied to operands of type 'string' and 'int'

Question

I'm quite new to C# and had been looking for solutions regarding converting string to integer using Int32.Parse, Int32.TryParse, Convert.Int32 etc. However I couldn't find the right solutions to get near what I wanted. I had found a similar post here: Operator '>=' cannot be applied to operands of type 'string' and 'string' , but still couldn't find the right solutions.

Here's a brief of what I'm trying to code.

1. Open an Excel file named "compare.xls", read file and write to a text file named "tline.txt"

2. Then open text file "tline.txt", read text line by line and only write to a text file named "mkmatlab.txt" with conditional statements. Conditional statement: If the number read from the line is 25 <= x <= 50, write it to "mkmatlab.txt" (only write to the file if it's an integer).

An idea of the contents in the Excel file:

A1..|  B1....... |  C1........ | D1........| E1........|      
0.1 |10.2000    |53.6000    |52.7894    |24.9608                                        
0.2 |26.8209    |55.0851    |56.4726    |35.8431                                    
0.3 |10.1009    |56.0314    |56.5013    |27.8922                                    
0.4 |17.7008    |60.0054    |59.7650    |37.8018    

*The symbol .. and | is just to act as spacing here, the Excel file or text file doesn't contain any of these symbols.

Explanations: First row contain A1 to E1. For Column A1 contain 0.1 to 0.4, and so on for column B1 to E1.

I have place comment on the line

if (words1[t] >= 25 && words1[t] <= 50)

where I need help with.

StreamReader fidin = File.OpenText(@"C:\Users\Student\Downloads\compare.xls");
StreamWriter tline = File.CreateText(@"C:\Users\Student\Downloads\tline.txt"); 

string F = fidin.ReadToEnd();
fidin.Close();

string[] words = F.Split(';');
Array.Sort(words);

for (int f = 0; f < words.Length; f++)
     tline.WriteLine(words[f]);
tline.Close();

StreamReader tline1 = File.OpenText(@"C:\Users\Student\Downloads\tline.txt");
StreamWriter fidout = File.CreateText(@"C:\Users\Student\Downloads\mkmatlab.txt");

string T = tline1.ReadToEnd();
            tline1.Close();

            string[] words1 = T.Split(';');
            Array.Sort(words1);

            int counter = 0;
            string line;

            while ((line = tline1.ReadLine()) != null)
            {
                System.Console.WriteLine(line);
                fidout.WriteLine(line);
                counter++;
                Console.ReadKey();
            }

Answer 1

Your values inside your excel file looks like double instead of int, so, you might want to consider to parse it double instead of int like;

double myDoubleWord = double.Parse(words1[t]);
if (myDoubleWord >= 25 && myDoubleWord <= 50) 

Comparing double with integers is fine with >= and <= operators.

Also be aware the cultural difference, since your values has . as a NumberDecimalSeparator, double.Parse uses your CurrentCulture settings which might not fit for your values.

Answer 2

Here is a good solution for parsing numbers.

if (int.TryParse(words1[t], out int num))  
{ 
     //we see test if the string is an number and if it is wi output is as a new int.
     if (num >= 25 && num <= 50) //now we can safely do your int comparison without number
     {
         fidout.WriteLine(words1[t]);
     }
}
else //if however our string wasn't capable of being an int we do something else
Console.WriteLine("couldn't parse string ");