Question

I have this code in C# Win Forms, which compares some numbers but it gives me following error:

InvalidCastException

Invalid cast from “Char” to “single”.

I dont understand this error.. eny enlightment would be nice 🙂

the error come in this line

float old_list_diff = Convert.ToSingle(ReadLine[0]) - Convert.ToSingle(ReadLine[i+1]);

here is my full code.:

private void button7_Click(object sender, EventArgs e)
{
  listBox1.Items.Clear();
  StreamReader SR = new StreamReader(Application.StartupPath + @"\old_Score_list.txt");
  string ReadLine = SR.ReadToEnd();

  for (int i = 0; i < 14; i++)
  {
      float new_list_diff = Convert.ToSingle(Score_list.Items[0]) - Convert.ToSingle(Score_list.Items[i+1]);
      float old_list_diff = Convert.ToSingle(ReadLine[0]) - Convert.ToSingle(ReadLine[i+1]);
      //int old_list_diff = 20;

      //skifter farve efter sidste i
      if (new_list_diff > old_list_diff == true)
      {
          //listBox1.ForeColor = Color.Green;
          listBox1.Items.Add("?");
      }
      else
      {
          //listBox1.ForeColor = Color.Red;
          listBox1.Items.Add("?");
      }
  }
}

Answer 1

string ReadLine = SR.ReadToEnd();

Gives you a big string of the whole file.

ReadLine[0]

Gives you the first character, so maybe just ‘0’ or just ‘1’. That can’t be cast to a float.

I’d guess you wanted:

string[] lines = SR.ReadLines();

Which would give you an array of strings, one for each line. Then lines[0] would indeed be (if in the correct format) a string you could convert to a float, but I’m having to guess a bit about what you actually want.