Use Regular Expression to Check the input for a TextBox : TextBox « GUI Windows Forms « C# / CSharp Tutorial

1. C# / CSharp Tutorial
2. GUI Windows Forms
3. TextBox

using System;
using System.Windows.Forms;
using System.Text.RegularExpressions;

public class TextBoxValidationRegex : Form
{
    public TextBoxValidationRegex()
    {
        this.components = new System.ComponentModel.Container();
        this.Button1 = new System.Windows.Forms.Button();
        this.errProvider = new System.Windows.Forms.ErrorProvider(this.components);
        this.Label3 = new System.Windows.Forms.Label();
        this.txtEmail = new System.Windows.Forms.TextBox();
        ((System.ComponentModel.ISupportInitialize)(this.errProvider)).BeginInit();
        this.SuspendLayout();

        this.Button1.Location = new System.Drawing.Point(212, 80);
        this.Button1.Name = "Button1";
        this.Button1.Size = new System.Drawing.Size(76, 24);
        this.Button1.TabIndex = 12;
        this.Button1.Text = "OK";
        this.Button1.Click += new System.EventHandler(this.Button1_Click);

        this.errProvider.ContainerControl = this;
        this.errProvider.DataMember = "";

        this.Label3.Location = new System.Drawing.Point(24, 24);
        this.Label3.Size = new System.Drawing.Size(40, 16);
        this.Label3.Text = "Email:";

        this.txtEmail.Location = new System.Drawing.Point(68, 20);
        this.txtEmail.Size = new System.Drawing.Size(220, 21);
        this.txtEmail.Leave += new System.EventHandler(this.txtEmail_Leave);

        this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 13F);
        this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
        this.ClientSize = new System.Drawing.Size(328, 126);
        this.Controls.Add(this.Label3);
        this.Controls.Add(this.txtEmail);
        this.Controls.Add(this.Button1);
        this.Font = new System.Drawing.Font("Tahoma", 8.25F, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, ((byte)(0)));
        ((System.ComponentModel.ISupportInitialize)(this.errProvider)).EndInit();
        this.ResumeLayout(false);
        this.PerformLayout();

    }

    private void Button1_Click(object sender, EventArgs e)
    {
        string errorText = "";

        foreach (Control ctrl in this.Controls)
        {
            if (errProvider.GetError(ctrl) != "")
            {
                errorText += "   * " + errProvider.GetError(ctrl) + "\n";
                
            }
            MessageBox.Show("Errors:" +errorText, "Invalid Input", MessageBoxButtons.OK, MessageBoxIcon.Warning);
        }
    }

    private void txtEmail_Leave(object sender, EventArgs e)
    {
        Regex regex;
        regex = new Regex(@"^[\w-]+@([\w-]+\.)+[\w-]+$");

        Control ctrl = (Control)sender;
        if (regex.IsMatch(ctrl.Text) || ctrl.Text == "")
        {
            errProvider.SetError(ctrl, "");
        }
        else
        {
            errProvider.SetError(ctrl, "This is not a valid email address.");
        }
    }

    [STAThread]
    public static void Main(string[] args)
    {
        Application.Run(new TextBoxValidationRegex());
    }
    private System.Windows.Forms.Button Button1;
    private System.Windows.Forms.ErrorProvider errProvider;
    private System.Windows.Forms.Label Label3;
    private System.Windows.Forms.TextBox txtEmail;

    private System.ComponentModel.IContainer components = null;

}

23.17.TextBox
	23.17.1.	Get input value from TextBox and display it vis a messagebox
	23.17.2.	TextBox key pressed event
	23.17.3.	TextBox Modified and TextChanged
	23.17.4.	TextBox: Multiline and BorderStyle
	23.17.5.	TextBox Keyevent hander
	23.17.6.	TextBox cancel event
	23.17.7.	Count lines in the TextBox and read text in TextBox line by line
	23.17.8.	TextBox selection
	23.17.9.	TextBox validation
	23.17.10.	Add ContextMenu to TextBox
	23.17.11.	Use Regular Expression to Check the input for a TextBox
	23.17.12.	Multiline TextBox
	23.17.13.	Simple Editor