I have a TextBoxD1.Text and I want to convert it to an int to store it in a database.
How can I do this?
Try this:
int x = Int32.Parse(TextBoxD1.Text);
or better yet:
int x = 0;
Int32.TryParse(TextBoxD1.Text, out x);
Also, since Int32.TryParse returns a bool you can use its return value to make decisions about the results of the parsing attempt:
int x = 0;
if (Int32.TryParse(TextBoxD1.Text, out x))
{
// you know that the parsing attempt
// was successful
}
If you are curious, the difference between Parse and TryParse is best summed up like this:
The TryParse method is like the Parse
method, except the TryParse method
does not throw an exception if the
conversion fails. It eliminates the
need to use exception handling to test
for a FormatException in the event
that s is invalid and cannot be
successfully parsed. - MSDN
Convert.ToInt32( TextBoxD1.Text );
Use this if you feel confident that the contents of the text box is a valid int. A safer option is
int val = 0;
Int32.TryParse( TextBoxD1.Text, out val );
This will provide you with some default value you can use. Int32.TryParse also returns a Boolean value indicating whether it was able to parse or not, so you can even use it as the condition of an if statement.
if( Int32.TryParse( TextBoxD1.Text, out val ){
DoSomething(..);
} else {
HandleBadInput(..);
}
int.TryParse()
It won't throw if the text is not numeric.
int myInt = int.Parse(TextBoxD1.Text)
Another way would be:
bool isConvertible = false;
int myInt = 0;
isConvertible = int.TryParse(TextBoxD1.Text, out myInt);
The difference between the two is that the first one would throw an exception if the value in your textbox can't be converted, whereas the second one would just return false.
Be careful when using Convert.ToInt32() on a char!
It will return the UTF-16 code of the character!
If you access the string only in a certain position using the [i] indexing operator, it will return a char and not a string!
String input = "123678";
^
|
int indexOfSeven = 4;
int x = Convert.ToInt32(input[indexOfSeven]); // Returns 55
int x = Convert.ToInt32(input[indexOfSeven].toString()); // Returns 7
You need to parse the string, and you also need to ensure that it is truly in the format of an integer.
The easiest way is this:
int parsedInt = 0;
if (int.TryParse(TextBoxD1.Text, out parsedInt))
{
// Code for if the string was valid
}
else
{
// Code for if the string was invalid
}
int x = 0;
int.TryParse(TextBoxD1.Text, out x);
The TryParse statement returns a boolean representing whether the parse has succeeded or not. If it succeeded, the parsed value is stored into the second parameter.
See Int32.TryParse Method (String, Int32) for more detailed information.
Enjoy it...
int i = 0;
string s = "123";
i =int.Parse(s);
i = Convert.ToInt32(s);
While there are already many solutions here that describe int.Parse, there's something important missing in all the answers. Typically, the string representations of numeric values differ by culture. Elements of numeric strings such as currency symbols, group (or thousands) separators, and decimal separators all vary by culture.
If you want to create a robust way to parse a string to an integer, it's therefore important to take the culture information into account. If you don't, the current culture settings will be used. That might give a user a pretty nasty surprise -- or even worse, if you're parsing file formats. If you just want English parsing, it's best to simply make it explicit, by specifying the culture settings to use:
var culture = CultureInfo.GetCulture("en-US");
int result = 0;
if (int.TryParse(myString, NumberStyles.Integer, culture, out result))
{
// use result...
}
For more information, read up on CultureInfo, specifically NumberFormatInfo on MSDN.
int x = Int32.TryParse(TextBoxD1.Text, out x) ? x : 0;
You can write your own extension method
public static class IntegerExtensions
{
public static int ParseInt(this string value, int defaultValue = 0)
{
int parsedValue;
if (int.TryParse(value, out parsedValue))
{
return parsedValue;
}
return defaultValue;
}
public static int? ParseNullableInt(this string value)
{
if (string.IsNullOrEmpty(value))
{
return null;
}
return value.ParseInt();
}
}
And wherever in code just call
int myNumber = someString.ParseInt(); // Returns value or 0
int age = someString.ParseInt(18); // With default value 18
int? userId = someString.ParseNullableInt(); // Returns value or null
In this concrete case
int yourValue = TextBoxD1.Text.ParseInt();
As explained in the TryParse documentation, TryParse() returns a Boolean which indicates that a valid number was found:
bool success = Int32.TryParse(TextBoxD1.Text, out val);
if (success)
{
// Put val in database
}
else
{
// Handle the case that the string doesn't contain a valid number
}
You can convert string to int many different type methods in C#
First one is mostly use :
string test = "123";
int x = Convert.ToInt16(test);
if int value is higher you should use int32 type.
Second one:
int x = int.Parse(text);
if you want to error check, you can use TryParse method. In below I add nullable type;
int i=0;
Int32.TryParse(text, out i) ? i : (int?)null);
Enjoy your codes....
Conversion of string to int can be done for: int, Int32, Int64 and other data types reflecting integer data types in .NET
Below example shows this conversion:
This shows (for info) data adapter element initialized to int value. The same can be done directly like,
int xxiiqVal = Int32.Parse(strNabcd);
Ex.
string strNii = "";
UsrDataAdapter.SelectCommand.Parameters["#Nii"].Value = Int32.Parse(strNii );
Link to see this demo.
int i = Convert.ToInt32(TextBoxD1.Text);
//May be quite some time ago but I just want throw in some line for any one who may still need it
int intValue;
string strValue = "2021";
try
{
intValue = Convert.ToInt32(strValue);
}
catch
{
//Default Value if conversion fails OR return specified error
// Example
intValue = 2000;
}
You can use either,
int i = Convert.ToInt32(TextBoxD1.Text);
or
int i = int.Parse(TextBoxD1.Text);
You can do like below without TryParse or inbuilt functions:
static int convertToInt(string a)
{
int x = 0;
for (int i = 0; i < a.Length; i++)
{
int temp = a[i] - '0';
if (temp != 0)
{
x += temp * (int)Math.Pow(10, (a.Length - (i+1)));
}
}
return x;
}
You also may use an extension method, so it will be more readable (although everybody is already used to the regular Parse functions).
public static class StringExtensions
{
/// <summary>
/// Converts a string to int.
/// </summary>
/// <param name="value">The string to convert.</param>
/// <returns>The converted integer.</returns>
public static int ParseToInt32(this string value)
{
return int.Parse(value);
}
/// <summary>
/// Checks whether the value is integer.
/// </summary>
/// <param name="value">The string to check.</param>
/// <param name="result">The out int parameter.</param>
/// <returns>true if the value is an integer; otherwise, false.</returns>
public static bool TryParseToInt32(this string value, out int result)
{
return int.TryParse(value, out result);
}
}
And then you can call it that way:
If you are sure that your string is an integer, like "50".
int num = TextBoxD1.Text.ParseToInt32();
If you are not sure and want to prevent crashes.
int num;
if (TextBoxD1.Text.TryParseToInt32(out num))
{
//The parse was successful, the num has the parsed value.
}
To make it more dynamic, so you can parse it also to double, float, etc., you can make a generic extension.
You can convert a string to int in C# using:
Functions of convert class i.e. Convert.ToInt16(), Convert.ToInt32(), Convert.ToInt64() or by using Parse and TryParse Functions. Examples are given here.
This would do
string x = TextBoxD1.Text;
int xi = Convert.ToInt32(x);
Or you can use
int xi = Int32.Parse(x);
Refer Microsoft Developer Network for more information
You can convert string to an integer value with the help of parse method.
Eg:
int val = Int32.parse(stringToBeParsed);
int x = Int32.parse(1234);
In C# v.7 you could use an inline out parameter, without an additional variable declaration:
int.TryParse(TextBoxD1.Text, out int x);
The way I always do this is like this:
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
namespace example_string_to_int
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
string a = textBox1.Text;
// This turns the text in text box 1 into a string
int b;
if (!int.TryParse(a, out b))
{
MessageBox.Show("This is not a number");
}
else
{
textBox2.Text = a+" is a number" ;
}
// Then this 'if' statement says if the string is not a number, display an error, else now you will have an integer.
}
}
}
This is how I would do it.
All the above answers are good but for information, we can use int.TryParse which is safe to convert string to int, for example
// TryParse returns true if the conversion succeeded
// and stores the result in j.
int j;
if (Int32.TryParse("-105", out j))
Console.WriteLine(j);
else
Console.WriteLine("String could not be parsed.");
// Output: -105
TryParse never throws an exception—even on invalid input and null. It is overall preferable to int.Parse in most program contexts.
Source: How to convert string to int in C#? (With Difference between Int.Parse and Int.TryParse)
In case you know the string is an integer do:
int value = int.Parse(TextBoxD1.Text);
In case you don't know the string is an integer do it safely with TryParse.
In C# 7.0 you can use inline variable declaration.
If parse successes - value = its parsed value.
If parse fails - value = 0.
Code:
if (int.TryParse(TextBoxD1.Text, out int value))
{
// Parse succeed
}
Drawback:
You cannot differentiate between a 0 value and a non parsed value.
Here is the version of doing it via an Extension Method that has an option to set the default value as well, if the converting fails. In fact, this is what I used to convert a string input to any convertible type:
using System;
using System.ComponentModel;
public static class StringExtensions
{
public static TOutput AsOrDefault<TOutput>(this string input, TOutput defaultValue = default)
where TOutput : IConvertible
{
TOutput output = defaultValue;
try
{
var converter = TypeDescriptor.GetConverter(typeof(TOutput));
if (converter != null)
{
output = (TOutput)converter.ConvertFromString(input);
}
}
catch { }
return output;
}
}
For my usage, I limited the output to be one of the convertible types: https://learn.microsoft.com/en-us/dotnet/api/system.iconvertible?view=net-5.0. I don't need crazy logics to convert a string to a class, for example.
To use it to convert a string to int:
using FluentAssertions;
using Xunit;
[Theory]
[InlineData("0", 0)]
[InlineData("1", 1)]
[InlineData("123", 123)]
[InlineData("-123", -123)]
public void ValidStringWithNoDefaultValue_ReturnsExpectedResult(string input, int expectedResult)
{
var result = input.AsOrDefault<int>();
result.Should().Be(expectedResult);
}
[Theory]
[InlineData("0", 999, 0)]
[InlineData("1", 999, 1)]
[InlineData("123", 999, 123)]
[InlineData("-123", -999, -123)]
public void ValidStringWithDefaultValue_ReturnsExpectedResult(string input, int defaultValue, int expectedResult)
{
var result = input.AsOrDefault(defaultValue);
result.Should().Be(expectedResult);
}
[Theory]
[InlineData("")]
[InlineData(" ")]
[InlineData("abc")]
public void InvalidStringWithNoDefaultValue_ReturnsIntegerDefault(string input)
{
var result = input.AsOrDefault<int>();
result.Should().Be(default(int));
}
[Theory]
[InlineData("", 0)]
[InlineData(" ", 1)]
[InlineData("abc", 234)]
public void InvalidStringWithDefaultValue_ReturnsDefaultValue(string input, int defaultValue)
{
var result = input.AsOrDefault(defaultValue);
result.Should().Be(defaultValue);
}
METHOD 1
int TheAnswer1 = 0;
bool Success = Int32.TryParse("42", out TheAnswer1);
if (!Success) {
Console.WriteLine("String not Convertable to an Integer");
}
METHOD 2
int TheAnswer2 = 0;
try {
TheAnswer2 = Int32.Parse("42");
}
catch {
Console.WriteLine("String not Convertable to an Integer");
}
METHOD 3
int TheAnswer3 = 0;
try {
TheAnswer3 = Int32.Parse("42");
}
catch (FormatException) {
Console.WriteLine("String not in the correct format for an Integer");
}
catch (ArgumentNullException) {
Console.WriteLine("String is null");
}
catch (OverflowException) {
Console.WriteLine("String represents a number less than"
+ "MinValue or greater than MaxValue");
}
You can try the following. It will work:
int x = Convert.ToInt32(TextBoxD1.Text);
The string value in the variable TextBoxD1.Text will be converted into Int32 and will be stored in x.
While I agree on using the TryParse method, a lot of people dislike the use of out parameter (myself included). With tuple support having been added to C#, an alternative is to create an extension method that will limit the number of times you use out to a single instance:
public static class StringExtensions
{
public static (int result, bool canParse) TryParse(this string s)
{
int res;
var valid = int.TryParse(s, out res);
return (result: res, canParse: valid);
}
}
(Source: C# how to convert a string to int)
I just want to know, whether a String variable contains a parsable positive integer value. I do NOT want to parse the value right now.
Currently I am doing:
int parsedId;
if (
(String.IsNullOrEmpty(myStringVariable) ||
(!uint.TryParse(myStringVariable, out parsedId))
)
{//..show error message}
This is ugly - How to be more concise?
Note: I know about extension methods, but I wonder if there is something built-in.
You could use char.IsDigit:
bool isIntString = "your string".All(char.IsDigit)
Will return true if the string is a number
bool containsInt = "your string".Any(char.IsDigit)
Will return true if the string contains a digit
Assuming you want to check that all characters in the string are digits, you could use the Enumerable.All Extension Method with the Char.IsDigit Method as follows:
bool allCharactersInStringAreDigits = myStringVariable.All(char.IsDigit);
Maybe this can help
string input = "hello123world";
bool isDigitPresent = input.Any(c => char.IsDigit(c));
answer from msdn.
You can check if string contains numbers only:
Regex.IsMatch(myStringVariable, #"^-?\d+$")
But number can be bigger than Int32.MaxValue or less than Int32.MinValue - you should keep that in mind.
Another option - create extension method and move ugly code there:
public static bool IsInteger(this string s)
{
if (String.IsNullOrEmpty(s))
return false;
int i;
return Int32.TryParse(s, out i);
}
That will make your code more clean:
if (myStringVariable.IsInteger())
// ...
This work for me.
("your string goes here").All(char.IsDigit)
Sorry, didn't quite get your question. So something like this?
str.ToCharArray().Any(char.IsDigit);
Or does the value have to be an integer completely, without any additional strings?
if(str.ToCharArray().All(char.IsDigit(c));
string text = Console.ReadLine();
bool isNumber = false;
for (int i = 0; i < text.Length; i++)
{
if (char.IsDigit(text[i]))
{
isNumber = true;
break;
}
}
if (isNumber)
{
Console.WriteLine("Text contains number.");
}
else
{
Console.WriteLine("Text doesn't contain number.");
}
Console.ReadKey();
Or Linq:
string text = Console.ReadLine();
bool isNumberOccurance =text.Any(letter => char.IsDigit(letter));
Console.WriteLine("{0}",isDigitPresent ? "Text contains number." : "Text doesn't contain number.");
Console.ReadKey();
The answer seems to be just no.
Although there are many good other answers, they either just hide the uglyness (which I did not ask for) or introduce new problems (edge cases).
I have a little problem with a simple console application in which i would like to detect if the user inputs a correctly formatted numerical value.
That is, values such as 1212sss or anything like asjkq12323 or a single character is not accepted. I would like to only accept pure integer values.
Here is what i have tried
bool detectNumber(string s)
{
int value=0;
Int.TryParse(s,out value);
return (value!=0)?true:false;
}
I appreciate any help. Thank you soooo much,,,,,
TryParse returns a boolean. Check that, not the value passed via the out parameter.
if( int.TryParse( s, out value ) )
{
// do something
}
Or just:
return int.TryParse( s, out value );
Incidentally, it is not necessary to initialize a value passed using the out keyword. The method declaring the parameter must initialize it before returning.
int foo; // legal
int.TryParse( "123", out foo );
All BCL "Try" methods follow the same convention (such as double.TryParse() for floating point numbers, as #gdoron mentioned in the comments).
And for the curious, source code for the underlying library which implements int.TryParse().
int value = 0;
bool ok = int.TryParse(s, out value);
return ok;
string line = Console.ReadLine();
int value;
if (int.TryParse(line, out value))
{
Console.WriteLine("Integer here!");
}
else
{
Console.WriteLine("Not an integer!");
}
There are several ways to test for only numeric numbers:
first of all, never use Int because of it's maximum value, either use int or Int32.
Parse
int result;
if (int.TryParse("123", out result))
{
Debug.WriteLine("Valid integer: " + result);
}
else
{
Debug.WriteLine("Not a valid integer");
}
Convert.ToInt32()
// throws ArgumentNullExceptionint
result1 = Int32.Parse(null);
// doesn't throw an exception, returns 0
int result2 = Convert.ToInt32(null);
IsNumeric()
using Microsoft.VisualBasic;
// ......
bool result = Information.IsNumeric("123");
Pattern Matching
string strToTest = "123";
Regex reNum = new Regex(#"^\d+$");
bool isNumeric = reNum.Match(strToTest).Success;
Your code works normal, you can only refactor it a bit. Following code is shorter but does exactly the same:
static bool IsInt32(string s)
{
int value;
return Int32.TryParse(s, out value);
}
I have a input field that is supposed to take numbers only.
How can I validate the string?
Would this be ok:
string s = "12345";
double num;
bool isNum = double.TryParse(s, out num);
Or does .Net have a solution for this?
Single one line answer. Does the job.
string s = "1234";
if (s.ToCharArray().All(x => Char.IsDigit(x)))
{
console.writeline("its numeric");
}
else
{
console.writeline("NOT numeric");
}
What you've done looks correct.
You could also create an extension method to make it easier:
public static bool IsNumeric(this object _obj)
{
if (_obj == null)
return false;
bool isNum;
double retNum;
isNum = Double.TryParse(Convert.ToString(_obj), System.Globalization.NumberStyles.Any, System.Globalization.NumberFormatInfo.InvariantInfo, out retNum);
return isNum;
}
So then you could do:
s.IsNumeric()
your solution is ok but you could create a method that does this job for you. Bear in mind it may not work for other countries because of the culture. What about something like the below?
public bool isNumeric(string val, System.Globalization.NumberStyles NumberStyle)
{
Double result;
return Double.TryParse(val,NumberStyle,
System.Globalization.CultureInfo.CurrentCulture,out result);
}
VB.NET has the IsNumeric function but what you have there is the way to do that in C#. To make it available app-wide just write an extension method on string
public static bool IsNumeric(this string input)
{
if (string.IsNullOrWhitespace(input))
return false;
double result;
return Double.TryParse(input, out result);
}
You can use Regular Expression Validators in ASP.NET to constrain the input.
Why don't you try to validate the input through the UI? I don't know if you're using asp.net, if so, the RegularExpressionValidator is normally a valid solution for this. (http://www.w3schools.com/aspnet/control_regularexpvalidator.asp). Hope this helps!
I need to check if a string contains only digits. How could I achieve this in C#?
string s = "123" → valid
string s = "123.67" → valid
string s = "123F" → invalid
Is there any function like IsNumeric?
double n;
if (Double.TryParse("128337.812738", out n)) {
// ok
}
works assuming the number doesn't overflow a double
for a huge string, try the regexp:
if (Regex.Match(str, #"^[0-9]+(\.[0-9]+)?$")) {
// ok
}
add in scientific notation (e/E) or +/- signs if needed...
Taken from MSDN (How to implement Visual Basic .NET IsNumeric functionality by using Visual C#):
// IsNumeric Function
static bool IsNumeric(object Expression)
{
// Variable to collect the Return value of the TryParse method.
bool isNum;
// Define variable to collect out parameter of the TryParse method. If the conversion fails, the out parameter is zero.
double retNum;
// The TryParse method converts a string in a specified style and culture-specific format to its double-precision floating point number equivalent.
// The TryParse method does not generate an exception if the conversion fails. If the conversion passes, True is returned. If it does not, False is returned.
isNum = Double.TryParse(Convert.ToString(Expression), System.Globalization.NumberStyles.Any, System.Globalization.NumberFormatInfo.InvariantInfo, out retNum );
return isNum;
}
You can use double.TryParse
string value;
double number;
if (Double.TryParse(value, out number))
Console.WriteLine("valid");
else
Console.WriteLine("invalid");
This should work no matter how long the string is:
string s = "12345";
bool iAllNumbers = s.ToCharArray ().All (ch => Char.IsDigit (ch) || ch == '.');
Using regular expressions is the easiest way (but not the quickest):
bool isNumeric = Regex.IsMatch(s,#"^(\+|-)?\d+(\.\d+)?$");
As stated above you can use double.tryParse
If you don't like that (for some reason), you can write your own extension method:
public static class ExtensionMethods
{
public static bool isNumeric (this string str)
{
for (int i = 0; i < str.Length; i++ )
{
if ((str[i] == '.') || (str[i] == ',')) continue; //Decide what is valid, decimal point or decimal coma
if ((str[i] < '0') || (str[i] > '9')) return false;
}
return true;
}
}
Usage:
string mystring = "123456abcd123";
if (mystring.isNumeric()) MessageBox.Show("The input string is a number.");
else MessageBox.Show("The input string is not a number.");
Input :
123456abcd123
123.6
Output:
false
true
I think you can use Regular Expressions, in the Regex class
Regex.IsMatch( yourStr, "\d" )
or something like that off the top of my head.
Or you could use the Parse method int.Parse( ... )
If you are receiving the string as a parameter the more flexible way would be to use regex as described in the other posts.
If you get the input from the user, you can just hook on the KeyDown event and ignore all keys that are not numbers. This way you'll be sure that you have only digits.
This should work:
bool isNum = Integer.TryParse(Str, out Num);