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DataGridViewComboBoxColumn Class

Note: This class is new in the .NET Framework version 2.0.

Represents a column of DataGridViewComboBoxCell objects.

Namespace: System.Windows.Forms
Assembly: System.Windows.Forms (in system.windows.forms.dll)

public class DataGridViewComboBoxColumn : DataGridViewColumn
public class DataGridViewComboBoxColumn extends DataGridViewColumn
public class DataGridViewComboBoxColumn extends DataGridViewColumn

The DataGridViewComboBoxColumn class is a specialized type of DataGridViewColumn used to logically host cells that enable selection and editing. A DataGridViewComboBoxColumn has an associated DataGridViewComboBoxCell in every DataGridViewRow that intersects it.

The following steps describe a common way to use this class:

  1. Create a DataGridView.

  2. Set the DataSource property of the DataGridView.

  3. Create a DataGridViewComboBoxColumn.

  4. If the data source contains multiple properties or columns, set the DataPropertyName property to the name of the property or column for populating the cell values.

  5. Use the DataSource or Items properties to establish the selections.

  6. Use the ValueMember and DisplayMember properties to establish a mapping between cell values and what will be displayed on the screen.

The DataGridViewComboBoxColumn will only work properly if there is a mapping between all its cell values that are populated by the DataGridView.DataSource property and the range of choices populated either by the DataSource property or the Items property. If this mapping doesn't exist, the message "An Error happened Formatting, Display" will appear when the column is in view.

The default sort mode for this column type is NotSortable.

Notes to Inheritors When you derive from DataGridViewComboBoxColumn and add new properties to the derived class, be sure to override the Clone method to copy the new properties during cloning operations. You should also call the base class's Clone method so that the properties of the base class are copied to the new cell.

The following code example demonstrates how to use a DataGridViewComboBoxColumn to aid in entering data into the TitleOfCourtesy column.

using System;
using System.Data;
using System.Data.SqlClient;
using System.Windows.Forms;
using System.Collections.Generic;
using System.Drawing;

public class Employees : Form
{
    private DataGridView DataGridView1 = new DataGridView();
    private DataGridView DataGridView2 = new DataGridView();

    [STAThread]
    public static void Main()
    {
        try
        {
            Application.EnableVisualStyles();
            Application.Run(new Employees());
        }
        catch (Exception e)
        {
            MessageBox.Show(e.Message + e.StackTrace);
        }
    }

    public Employees()
    {
        this.Load += new EventHandler(Form1_Load);
    }

    private void Form1_Load(System.Object sender, System.EventArgs e)
    {
        try
        {
            SetUpForm();
            SetUpDataGridView1();
            SetUpDataGridView2();
        }
        catch (SqlException)
        {
            MessageBox.Show("The connection string <"
                + connectionString
                + "> failed to connect.  Modify it "
                + "to connect to a Northwind database accessible to "
                + "your system.",
                "ERROR", MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
            Application.Exit();
        }
    }

    private void SetUpForm()
    {
        Size = new Size(800, 600);
        FlowLayoutPanel flowLayout = new FlowLayoutPanel();
        flowLayout.FlowDirection = FlowDirection.TopDown;
        flowLayout.Dock = DockStyle.Fill;
        Controls.Add(flowLayout);
        Text = "DataGridView columns demo";

        flowLayout.Controls.Add(DataGridView1);
        flowLayout.Controls.Add(DataGridView2);
    }

    private void SetUpDataGridView2()
    {
        DataGridView2.Dock = DockStyle.Bottom;
        DataGridView2.TopLeftHeaderCell.Value = "Sales Details";
        DataGridView2.RowHeadersWidthSizeMode = 
            DataGridViewRowHeadersWidthSizeMode.AutoSizeToAllHeaders;
    }

    private void SetUpDataGridView1()
    {
        DataGridView1.DataError += new 
            DataGridViewDataErrorEventHandler(DataGridView1_DataError);
        DataGridView1.CellContentClick += new 
            DataGridViewCellEventHandler(DataGridView1_CellContentClick);
        DataGridView1.CellValuePushed += new 
            DataGridViewCellValueEventHandler(DataGridView1_CellValuePushed);
        DataGridView1.CellValueNeeded += new 
            DataGridViewCellValueEventHandler(DataGridView1_CellValueNeeded);

        // Virtual mode is turned on so that the
        // unbound DataGridViewCheckBoxColumn will
        // keep its state when the bound columns are
        // sorted.       
        DataGridView1.VirtualMode = true;
        DataGridView1.AutoSize = true;
        DataGridView1.DataSource = Populate("SELECT * FROM Employees");
        DataGridView1.TopLeftHeaderCell.Value = "Employees";
        DataGridView1.RowHeadersWidthSizeMode = 
            DataGridViewRowHeadersWidthSizeMode.AutoSizeToAllHeaders;
        DataGridView1.ColumnHeadersHeightSizeMode = 
            DataGridViewColumnHeadersHeightSizeMode.AutoSize;
        DataGridView1.AutoSizeColumnsMode = 
            DataGridViewAutoSizeColumnsMode.AllCells;
        DataGridView1.AllowUserToAddRows = false;
        DataGridView1.AllowUserToDeleteRows = false;

        // The below autogenerated column is removed so 
        // a DataGridViewComboboxColumn could be used instead.
        DataGridView1.Columns.Remove(ColumnName.TitleOfCourtesy.ToString());
        DataGridView1.Columns.Remove(ColumnName.ReportsTo.ToString());

        AddLinkColumn();
        AddComboBoxColumns();
        AddButtonColumn();
        AddOutOfOfficeColumn();
    }

    // Using an enum provides some abstraction between column index
    // and column name along with compile time checking, and gives
    // a handy place to store the column names.
    enum ColumnName
    {
        EmployeeId,
        LastName,
        FirstName,
        Title,
        TitleOfCourtesy,
        BirthDate,
        HireDate,
        Address,
        City,
        Region,
        PostalCode,
        Country,
        HomePhone,
        Extension,
        Photo,
        Notes,
        ReportsTo,
        PhotoPath,
        OutOfOffice
    };

    private void AddComboBoxColumns()
    {
        DataGridViewComboBoxColumn comboboxColumn = new DataGridViewComboBoxColumn();
        comboboxColumn = CreateComboBoxColumn();
        SetAlternateChoicesUsingDataSource(ref comboboxColumn);
        comboboxColumn.HeaderText = "TitleOfCourtesy (via DataSource property)";
        DataGridView1.Columns.Insert(0, comboboxColumn);

        comboboxColumn = CreateComboBoxColumn();
        SetAlternateChoicesUsingItems(ref comboboxColumn);
        comboboxColumn.HeaderText = "TitleOfCourtesy (via Items property)";
        // Tack this example column onto the end.
        DataGridView1.Columns.Add(comboboxColumn);
    }

    private void AddLinkColumn()
    {
        DataGridViewLinkColumn links = new DataGridViewLinkColumn();

        links.HeaderText = ColumnName.ReportsTo.ToString();
        links.DataPropertyName = ColumnName.ReportsTo.ToString();
        links.ActiveLinkColor = Color.White;
        links.LinkBehavior = LinkBehavior.SystemDefault;
        links.LinkColor = Color.Blue;
        links.TrackVisitedState = true;
        links.VisitedLinkColor = Color.YellowGreen;

        DataGridView1.Columns.Add(links);
    }

    private static void SetAlternateChoicesUsingItems(
        ref DataGridViewComboBoxColumn comboboxColumn)
    {
        {
            comboboxColumn.Items.AddRange(
                new string[] { "Mr.", "Ms.", "Mrs.", "Dr." });
        }
    }

    private DataGridViewComboBoxColumn CreateComboBoxColumn()
    {
        DataGridViewComboBoxColumn column =
            new DataGridViewComboBoxColumn();
        {
            column.DataPropertyName = ColumnName.TitleOfCourtesy.ToString();
            column.HeaderText = ColumnName.TitleOfCourtesy.ToString();
            column.DropDownWidth = 160;
            column.Width = 90;
            column.MaxDropDownItems = 3;
            column.FlatStyle = FlatStyle.Flat;
        }
        return column;
    }

    private void SetAlternateChoicesUsingDataSource(ref DataGridViewComboBoxColumn comboboxColumn)
    {
        {
            comboboxColumn.DataSource = RetrieveAlternativeTitles();
            comboboxColumn.ValueMember = ColumnName.TitleOfCourtesy.ToString();
            comboboxColumn.DisplayMember = comboboxColumn.ValueMember;
        }
    }

    private DataTable RetrieveAlternativeTitles()
    {
        return Populate("SELECT distinct TitleOfCourtesy FROM Employees");
    }

    string connectionString =
        "Integrated Security=SSPI;Persist Security Info=False;" +
        "Initial Catalog=Northwind;Data Source=localhost";

    private DataTable Populate(string sqlCommand)
    {
        SqlConnection northwindConnection = new SqlConnection(connectionString);
        northwindConnection.Open();

        SqlCommand command = new SqlCommand(sqlCommand, northwindConnection);
        SqlDataAdapter adapter = new SqlDataAdapter();
        adapter.SelectCommand = command;

        DataTable table = new DataTable();
        table.Locale = System.Globalization.CultureInfo.InvariantCulture;
        adapter.Fill(table);

        return table;
    }

    private void AddButtonColumn()
    {
        DataGridViewButtonColumn buttons = new DataGridViewButtonColumn();
        {
            buttons.HeaderText = "Sales";
            buttons.Text = "Sales";
            buttons.UseColumnTextForButtonValue = true;
            buttons.AutoSizeMode =
                DataGridViewAutoSizeColumnMode.AllCells;
            buttons.FlatStyle = FlatStyle.Standard;
            buttons.CellTemplate.Style.BackColor = Color.Honeydew;
            buttons.DisplayIndex = 0;
        }

        DataGridView1.Columns.Add(buttons);

    }

    private void AddOutOfOfficeColumn()
    {
        DataGridViewCheckBoxColumn column = new DataGridViewCheckBoxColumn();
        {
            column.HeaderText = ColumnName.OutOfOffice.ToString();
            column.Name = ColumnName.OutOfOffice.ToString();
            column.AutoSizeMode = 
                DataGridViewAutoSizeColumnMode.DisplayedCells;
            column.FlatStyle = FlatStyle.Standard;
            column.ThreeState = true;
            column.CellTemplate = new DataGridViewCheckBoxCell();
            column.CellTemplate.Style.BackColor = Color.Beige;
        }

        DataGridView1.Columns.Insert(0, column);
    }

    private void PopulateSales(DataGridViewCellEventArgs buttonClick)
    {

        string employeeId = DataGridView1.Rows[buttonClick.RowIndex]
            .Cells[ColumnName.EmployeeId.ToString()].Value.ToString();
        DataGridView2.DataSource = Populate("SELECT * FROM Orders WHERE EmployeeId = " + employeeId);
    }

    #region "SQL Error handling"
    private void DataGridView1_DataError(object sender, DataGridViewDataErrorEventArgs anError)
    {

        MessageBox.Show("Error happened " + anError.Context.ToString());

        if (anError.Context == DataGridViewDataErrorContexts.Commit)
        {
            MessageBox.Show("Commit error");
        }
        if (anError.Context == DataGridViewDataErrorContexts.CurrentCellChange)
        {
            MessageBox.Show("Cell change");
        }
        if (anError.Context == DataGridViewDataErrorContexts.Parsing)
        {
            MessageBox.Show("parsing error");
        }
        if (anError.Context == DataGridViewDataErrorContexts.LeaveControl)
        {
            MessageBox.Show("leave control error");
        }

        if ((anError.Exception) is ConstraintException)
        {
            DataGridView view = (DataGridView)sender;
            view.Rows[anError.RowIndex].ErrorText = "an error";
            view.Rows[anError.RowIndex].Cells[anError.ColumnIndex].ErrorText = "an error";

            anError.ThrowException = false;
        }
    }
    #endregion

    private void DataGridView1_CellContentClick(object sender, DataGridViewCellEventArgs e)
    {

        if (IsANonHeaderLinkCell(e))
        {
            MoveToLinked(e);
        }
        else if (IsANonHeaderButtonCell(e))
        {
            PopulateSales(e);
        }
    }

    private void MoveToLinked(DataGridViewCellEventArgs e)
    {
        string employeeId;
        object value = DataGridView1.Rows[e.RowIndex].Cells[e.ColumnIndex].Value;
        if (value is DBNull) { return; }

        employeeId = value.ToString();
        DataGridViewCell boss = RetrieveSuperiorsLastNameCell(employeeId);
        if (boss != null)
        {
            DataGridView1.CurrentCell = boss;
        }
    }

    private bool IsANonHeaderLinkCell(DataGridViewCellEventArgs cellEvent)
    {
        if (DataGridView1.Columns[cellEvent.ColumnIndex] is
            DataGridViewLinkColumn &&
            cellEvent.RowIndex != -1)
        { return true; }
        else { return false; }
    }

    private bool IsANonHeaderButtonCell(DataGridViewCellEventArgs cellEvent)
    {
        if (DataGridView1.Columns[cellEvent.ColumnIndex] is
            DataGridViewButtonColumn &&
            cellEvent.RowIndex != -1)
        { return true; }
        else { return (false); }
    }

    private DataGridViewCell RetrieveSuperiorsLastNameCell(string employeeId)
    {

        foreach (DataGridViewRow row in DataGridView1.Rows)
        {
            if (row.IsNewRow) { return null; }
            if (row.Cells[ColumnName.EmployeeId.ToString()].Value.ToString().Equals(employeeId))
            {
                return row.Cells[ColumnName.LastName.ToString()];
            }
        }
        return null;
    }

    #region "checkbox state"
    Dictionary<string, bool> inOffice = new Dictionary<string, bool>();
    private void DataGridView1_CellValuePushed(object sender,
        DataGridViewCellValueEventArgs e)
    {
        if (IsCheckBoxColumn(e.ColumnIndex))
        {
            string employeeId = GetKey(e);
            if (!inOffice.ContainsKey(employeeId))
            {
                inOffice.Add(employeeId, (Boolean)e.Value);
            }
            else
            {
                inOffice[employeeId] = (Boolean)e.Value;
            }
        }
    }

    private string GetKey(DataGridViewCellValueEventArgs cell)
    {
        return DataGridView1.Rows[cell.RowIndex].
            Cells[ColumnName.EmployeeId.ToString()].Value.ToString();
    }

    private void DataGridView1_CellValueNeeded(object sender,
        DataGridViewCellValueEventArgs e)
    {

        if (IsCheckBoxColumn(e.ColumnIndex))
        {
            string employeeId = GetKey(e);
            if (!inOffice.ContainsKey(employeeId))
            {
                bool defaultValue = false;
                inOffice.Add(employeeId, defaultValue);
            }

            e.Value = inOffice[employeeId];
        }
    }

    private bool IsCheckBoxColumn(int columnIndex)
    {
        DataGridViewColumn outOfOfficeColumn =
            DataGridView1.Columns[ColumnName.OutOfOffice.ToString()];
        if (DataGridView1.Columns[columnIndex] == outOfOfficeColumn)
        {
            return true;
        }
        else
        {
            return false;
        }
    }
    #endregion
}

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Windows 98, Windows 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see System Requirements.

.NET Framework

Supported in: 2.0

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