Format (Change) DateTime in ASP.Net GridView BoundField column using C# and VB.Net

Hi RichardSa,

Use GrdiView OnRowDataBound event.

Check this example. Now please take its reference and correct your code.

Database

CREATE TABLE Times (Id INT IDENTITY,Start_Date VARCHAR(50))

HTML

<input type="datetime-local" id="startdate" runat="server" placeholder="e.g August 20, 2021 10:00:00 AM" />
<asp:Button Text="Save" runat="server" OnClick="OnSave" />
<hr />
<asp:GridView ID="gvDetails" runat="server" AutoGenerateColumns="false" OnRowDataBound="OnRowDataBound">
    <Columns>
        <asp:BoundField DataField="Start_Date" HeaderText="START DATE" ReadOnly="true" />
    </Columns>
</asp:GridView>

Namespaces

C#

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

VB.Net

Imports System.Configuration
Imports System.Data
Imports System.Data.SqlClient

Code

C#

protected void Page_Load(object sender, EventArgs e)
{
    if (!this.IsPostBack)
    {
        this.BindGrid();
    }
}

protected void OnSave(object sender, EventArgs e)
{
    string constr = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
    using (SqlConnection con = new SqlConnection(constr))
    {
        string query = "INSERT INTO Times VALUES(@StartDate)";
        using (SqlCommand cmd = new SqlCommand(query))
        {
            cmd.Connection = con;
            con.Open();
            cmd.Parameters.AddWithValue("@StartDate", startdate.Value);
            cmd.ExecuteNonQuery();
            con.Close();
        }
    }

    Response.Redirect(Request.Url.AbsoluteUri);
}

protected void OnRowDataBound(object sender, GridViewRowEventArgs e)
{
    if (e.Row.RowType == DataControlRowType.DataRow)
    {
        e.Row.Cells[0].Text = Convert.ToDateTime(e.Row.Cells[0].Text.Replace("T", " ")).ToString("d, MMMM yyyy hh:mm tt");
    }
}

private void BindGrid()
{
    string conString = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
    string query = "SELECT * FROM Times";
    using (SqlConnection con = new SqlConnection(conString))
    {
        SqlCommand cmd = new SqlCommand(query);
        using (SqlDataAdapter sda = new SqlDataAdapter())
        {
            cmd.Connection = con;
            sda.SelectCommand = cmd;
            using (DataTable dt = new DataTable())
            {
                sda.Fill(dt);
                gvDetails.DataSource = dt;
                gvDetails.DataBind();
            }
        }
    }
}

VB.Net

Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load
    If Not Me.IsPostBack Then
        Me.BindGrid()
    End If
End Sub

Protected Sub OnSave(ByVal sender As Object, ByVal e As EventArgs)
    Dim constr As String = ConfigurationManager.ConnectionStrings("constr").ConnectionString
    Using con As SqlConnection = New SqlConnection(constr)
        Dim query As String = "INSERT INTO Times VALUES(@StartDate)"
        Using cmd As SqlCommand = New SqlCommand(query)
            cmd.Connection = con
            con.Open()
            cmd.Parameters.AddWithValue("@StartDate", startdate.Value)
            cmd.ExecuteNonQuery()
            con.Close()
        End Using
    End Using

    Response.Redirect(Request.Url.AbsoluteUri)
End Sub

Protected Sub OnRowDataBound(ByVal sender As Object, ByVal e As GridViewRowEventArgs)
    If e.Row.RowType = DataControlRowType.DataRow Then
        e.Row.Cells(0).Text = Convert.ToDateTime(e.Row.Cells(0).Text.Replace("T", " ")).ToString("d, MMMM yyyy hh:mm tt")
    End If
End Sub

Private Sub BindGrid()
    Dim conString As String = ConfigurationManager.ConnectionStrings("constr").ConnectionString
    Dim query As String = "SELECT * FROM Times"
    Using con As SqlConnection = New SqlConnection(conString)
        Dim cmd As SqlCommand = New SqlCommand(query)
        Using sda As SqlDataAdapter = New SqlDataAdapter()
            cmd.Connection = con
            sda.SelectCommand = cmd
            Using dt As DataTable = New DataTable()
                sda.Fill(dt)
                gvDetails.DataSource = dt
                gvDetails.DataBind()
            End Using
        End Using
    End Using
End Sub

Screenshot