How to validate string,numbers etc.. whether can i use ASCII Range in C# like in C,C++ .

Raghu Janardhan

i am stuck..

need to find how to validate a basic string entry in Text box and even the integers or numbers..

have clue that i can use ASCII values to determine whether its string numbers etc.

requesting all to help.. open to any suggestions.

thanks
Raghu

4 Replies

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Vulpes14y ago
You can check for any printable ASCII value - letter, numbers or punctuation - with code such as this:

foreach(char c in textBox1.Text)
{
if (c < 32 || c > 126)
{
MessageBox("TextBox includes invalid characters, please amend");
textBox1.Focus();
return;
}
}

//for ASCII numbers only with this:

foreach(char c in textBox1.Text)
{
if (c < '0' || c > '9')
{
MessageBox("TextBox includes characters which are not digits, please amend");
textBox1.Focus();
return;
}
}

// for ASCII letters only with this:

foreach(char c in textBox1.Text.ToLower())
{
if (c < 'a' || c > 'z')
{
MessageBox("TextBox includes characters which are not letters, please amend");
textBox1.Focus();
return;
}
}

// or for ASCII letters or numbers only with this:

foreach(char c in textBox1.Text.ToLower())
{
if (!((c >= 'a' && c <= 'z') || (c >= '0' && c <= '9')))
{
MessageBox("TextBox includes characters which are not letters or digits, please amend");
textBox1.Focus();
return;
}
}
0
Raghu Janardhan14y ago
Whether ASCII values for alphabets and numbers.. so yield easy validation.. this one i want tocheck..
0
Vulpes14y ago
You can test whether a text string can be interpreted as a number using such methods as int.TryParse, double.TryParse and decimal.TryParse depending on whether you want to validate integers or numbers containing decimal points.

For example to validate an integer within some event handler:

int i;
bool isValid = int.TryParse(textBox1.Text, out i);

if (!isValid)
{
MessageBox.Show("Not a valid integer, please amend");
textBox1.Focus();
return;
}

// do something with 'i' which now contains a valid integer
0
Dorababu Meka14y ago
What kind of task you are having.. Can you input some valid expressions as per your requirement so that we can help
0