//=============
//Form1.Designer.cs
//===========
 
namespace WinDatagrid
{
    partial class Form1
    {
        /// <summary>
        /// Required designer variable.
        /// </summary>
        private System.ComponentModel.IContainer components = null;
 
        /// <summary>
        /// Clean up any resources being used.
        /// </summary>
        /// <param name="disposing">true if managed resources should be disposed; otherwise, false.</param>
        protected override void Dispose(bool disposing)
        {
            if (disposing && (components != null))
            {
                components.Dispose();
            }
            base.Dispose(disposing);
        }
 
        #region Windows Form Designer generated code
 
        /// <summary>
        /// Required method for Designer support - do not modify
        /// the contents of this method with the code editor.
        /// </summary>
        private void InitializeComponent()
        {
            this.dgvTest = new System.Windows.Forms.DataGridView();
            this.cbColumn = new System.Windows.Forms.ComboBox();
            this.btnAdd = new System.Windows.Forms.Button();
            ((System.ComponentModel.ISupportInitialize)(this.dgvTest)).BeginInit();
            this.SuspendLayout();
            // 
            // dgvTest
            // 
            this.dgvTest.ColumnHeadersHeightSizeMode = System.Windows.Forms.DataGridViewColumnHeadersHeightSizeMode.AutoSize;
            this.dgvTest.Location = new System.Drawing.Point(91, 95);
            this.dgvTest.Name = "dgvTest";
            this.dgvTest.Size = new System.Drawing.Size(389, 254);
            this.dgvTest.TabIndex = 0;
            // 
            // cbColumn
            // 
            this.cbColumn.FormattingEnabled = true;
            this.cbColumn.Location = new System.Drawing.Point(312, 51);
            this.cbColumn.Name = "cbColumn";
            this.cbColumn.Size = new System.Drawing.Size(168, 21);
            this.cbColumn.TabIndex = 1;
            this.cbColumn.SelectedIndexChanged += new System.EventHandler(this.cbColumn_SelectedIndexChanged);
            // 
            // btnAdd
            // 
            this.btnAdd.Location = new System.Drawing.Point(167, 49);
            this.btnAdd.Name = "btnAdd";
            this.btnAdd.Size = new System.Drawing.Size(113, 23);
            this.btnAdd.TabIndex = 2;
            this.btnAdd.Text = "Add New Column";
            this.btnAdd.UseVisualStyleBackColor = true;
            this.btnAdd.Click += new System.EventHandler(this.btnAdd_Click);
            // 
            // Form1
            // 
            this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 13F);
            this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
            this.ClientSize = new System.Drawing.Size(574, 390);
            this.Controls.Add(this.btnAdd);
            this.Controls.Add(this.cbColumn);
            this.Controls.Add(this.dgvTest);
            this.Name = "Form1";
            this.Text = "Form1";
            ((System.ComponentModel.ISupportInitialize)(this.dgvTest)).EndInit();
            this.ResumeLayout(false);
 
        }
 
        #endregion
 
        private System.Windows.Forms.DataGridView dgvTest;
        private System.Windows.Forms.ComboBox cbColumn;
        private System.Windows.Forms.Button btnAdd;
    }
}

//========
//Form1.cs
//========
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 WinDatagrid
{
    public partial class Form1 : Form
    {
        DataTable dt = new DataTable("dtGrid");
        public Form1()
        {
            InitializeComponent();
 
            cbColumn.Items.Add("UserName");
            cbColumn.Items.Add("Telephone");
            cbColumn.Items.Add("BirthDate");
            cbColumn.Items.Add("Address");
            cbColumn.Items.Add("E-Mail");
 
 
            dt.Columns.Add("UserName");
            dt.Columns.Add("Telephone");
            dt.Columns.Add("BirthDate");
            dgvTest.DataSource = dt;
 
 
        }
 
        private void cbColumn_SelectedIndexChanged(object sender, EventArgs e)
        {
            if (!dt.Columns.Contains(cbColumn.Text))
            {
                btnAdd.Enabled = true;
            }
            else
            {
                btnAdd.Enabled = false;
            }
        }
 
        private void btnAdd_Click(object sender, EventArgs e)
        {
            dt.Columns.Add(cbColumn.Text);
             btnAdd.Enabled = false;
        }
    }
}