Insert Please Select option as First Item in ComboBox in Windows Forms Application using C# and VB.Net

Full Code in C# and VB: Add (Insert) Default First Value in ComboBox in Windows Forms Application using C# and VB.Net

You have to do it in this way. Rather than inserting into the Combobox you need to add the value in the DataTable:

private void Form1_Load(object sender, EventArgs e)
{
    this.PopulateCombobox();
}

private void PopulateCombobox()
{
    DataTable dt = new DataTable();
    dt.Columns.Add("Id", typeof(int));
    dt.Columns.Add("Country", typeof(string));
    dt.Rows.Add(1, "USA");
    dt.Rows.Add(2, "England");
    dt.Rows.Add(3, "India");

    // Create a new row 
    DataRow dr = dt.NewRow();
    dr["Country"] = "Select";
    dr["Id"] = "0";
    // Insert it into the 0th index
    dt.Rows.InsertAt(dr, 0);

    this.cbbNames.ValueMember = "Id";
    this.cbbNames.DisplayMember = "Country";            
    this.cbbNames.DataSource = dt;     
}

VB:

Public Class Form1

    Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
        Me.PopulateCombobox()
    End Sub

    Private Sub PopulateCombobox()
        Dim dt As New DataTable()
        dt.Columns.Add("Id", GetType(Integer))
        dt.Columns.Add("Country", GetType(String))
        dt.Rows.Add(1, "USA")
        dt.Rows.Add(2, "England")
        dt.Rows.Add(3, "India")

        ' Create a new row
        Dim dr As DataRow = dt.NewRow()
        dr("Country") = "Select"
        dr("Id") = "0"
        ' Insert it into the 0th index
        dt.Rows.InsertAt(dr, 0)

        Me.cbbNames.ValueMember = "Id"
        Me.cbbNames.DisplayMember = "Country"
        Me.cbbNames.DataSource = dt
    End Sub

End Class

Image:

Thank You.