Retain Date format while exporting ASP.Net GridView to CSV using C# and VB.Net

Hi democloud

Please refer below smaple.

HTML

<asp:GridView runat="server" ID="GridView1" AutoGenerateColumns="false">
    <Columns>
        <asp:BoundField DataField="OrderID" HeaderText="OrderID" />
        <asp:BoundField DataField="OrderDate" HeaderText="OrderDate" />
        <asp:BoundField DataField="ShipCountry" HeaderText="ShipCountry" />
    </Columns>
</asp:GridView>
<asp:Button ID="Button1" Text="Export" runat="server" OnClick="btnToCSV_Click" />

Namespaces

C#

using System.Data.SqlClient;
using System.Configuration;
using System.Data;
using System.Text;

VB.Net

Imports System.Data.SqlClient
Imports System.IO
Imports System.Drawing
Imports System.Data

Code

C#

protected void Page_Load(object sender, EventArgs e)
{
    if (!this.IsPostBack)
    {
        string constr = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
        using (SqlConnection con = new SqlConnection(constr))
        {
            using (SqlCommand cmd = new SqlCommand("SELECT TOP 5  OrderID, OrderDate, ShipCountry FROM Orders", con))
            {
                using (SqlDataAdapter da = new SqlDataAdapter(cmd))
                {
                    DataTable dt = new DataTable();
                    da.Fill(dt);
                    GridView1.DataSource = dt;
                    GridView1.DataBind();
                    ViewState["Data"] = dt;
                }
            }
        }
    }
}

protected void btnToCSV_Click(object sender, EventArgs e)
{
    Response.Clear();
    Response.Buffer = true;
    Response.AddHeader("content-disposition", "attachment;filename=GridViewExport.csv");

    Response.Charset = "";
    Response.ContentType = "application/text";
    DataTable dt = ViewState["Data"] as DataTable;
    DataTable dt2 = new DataTable();
    for (int i = 0; i < dt.Columns.Count; i++)
    {
        dt2.Columns.Add(dt.Columns[i].ColumnName, typeof(string));
    }
    for (int i = 0; i < dt.Rows.Count; i++)
    {
        dt2.ImportRow(dt.Rows[i]);
        dt2.Rows[i]["OrderDate"] = Convert.ToDateTime(dt2.Rows[i]["OrderDate"]).ToString("yyyy/MM/dd");
    }

    this.GridView1.DataSource = dt2;
    this.GridView1.DataBind();

    StringBuilder sb = new StringBuilder();
    for (int k = 0; k < GridView1.Columns.Count; k++)
    {
        sb.Append(GridView1.Columns[k].HeaderText + ',');
    }
    sb.Append("\r\n");

    for (int i = 0; i < GridView1.Rows.Count; i++)
    {
        for (int k = 0; k < GridView1.Columns.Count; k++)
        {
            sb.Append(" " + GridView1.Rows[i].Cells[k].Text + ",");
        }
        sb.Append("\r\n");
    }
    Response.Output.Write(sb.ToString());
    Response.Flush();
    Response.End();
}

VB.Net

Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load
    If Not Me.IsPostBack Then
        Dim constr As String = ConfigurationManager.ConnectionStrings("constr").ConnectionString
        Using con As SqlConnection = New SqlConnection(constr)
            Using cmd As SqlCommand = New SqlCommand("SELECT TOP 5  OrderID, OrderDate, ShipCountry FROM Orders", con)
                Using da As SqlDataAdapter = New SqlDataAdapter(cmd)
                    Dim dt As DataTable = New DataTable()
                    da.Fill(dt)
                    GridView1.DataSource = dt
                    GridView1.DataBind()
                    ViewState("Data") = dt
                End Using
            End Using
        End Using
    End If
End Sub

Protected Sub btnToCSV_Click(ByVal sender As Object, ByVal e As EventArgs)
    Response.Clear()
    Response.Buffer = True
    Response.AddHeader("content-disposition", "attachment;filename=GridViewExport.csv")
    Response.Charset = ""
    Response.ContentType = "application/text"
    Dim dt As DataTable = TryCast(ViewState("Data"), DataTable)
    Dim dt2 As DataTable = New DataTable()
    For i As Integer = 0 To dt.Columns.Count - 1
        dt2.Columns.Add(dt.Columns(i).ColumnName, GetType(String))
    Next
    For i As Integer = 0 To dt.Rows.Count - 1
        dt2.ImportRow(dt.Rows(i))
        dt2.Rows(i)("OrderDate") = Convert.ToDateTime(dt2.Rows(i)("OrderDate")).ToString("yyyy/MM/dd")
    Next
    Me.GridView1.DataSource = dt2
    Me.GridView1.DataBind()
    Dim sb As StringBuilder = New StringBuilder()
    For k As Integer = 0 To GridView1.Columns.Count - 1
        sb.Append(GridView1.Columns(k).HeaderText + ","c)
    Next
    sb.Append(vbCrLf)
    For i As Integer = 0 To GridView1.Rows.Count - 1
        For k As Integer = 0 To GridView1.Columns.Count - 1
            sb.Append(" " & GridView1.Rows(i).Cells(k).Text & ",")
        Next
        sb.Append(vbCrLf)
    Next
    Response.Output.Write(sb.ToString())
    Response.Flush()
    Response.End()
End Sub

Screenshot