Save digital signature in Database and display in ASP.Net GridView using C# and VB.Net

Refer below Sample code For Your Reference and Implement It as Per Your Code Logic.

SQL

CREATE TABLE [File]
([Id] [int] IDENTITY(1,1) NOT NULL
,[FileName] [nvarchar](50) NULL) 
GO

HTML

<form id="form1" runat="server">
    <div>
        <div class="tools">
            <a href="#colors_sketch" data-tool="marker">Marker</a> <a href="#colors_sketch" data-tool="eraser">
                Eraser</a>
        </div>
        <br />
        <canvas id="colors_sketch" width="300px" height="100pxs">
    </canvas>
        <br />
        <br />
        <asp:TextBox ID="txtImageName" Width="150px" Height="30px" Placeholder="Enter Your Image Name"
            runat="server" />
        <asp:Button ID="btnSave" Text="Save Image" class="btnSuccess" OnClick="OnUpload"
            runat="server" />
        <hr />
        <asp:HiddenField ID="ImageVal" runat="server" />
        <br />
        <asp:GridView ID="GvImage" runat="server">
            <Columns>
                <asp:ImageField DataImageUrlField="FileName" HeaderText="Image" ControlStyle-Height="50"
                    ControlStyle-Width="50" />
            </Columns>
        </asp:GridView>
    </div>
    <div>
        <script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js"></script>
        <script src="https://cdn.rawgit.com/mobomo/sketch.js/master/lib/sketch.min.js" type="text/javascript"></script>
        <script type="text/javascript">
            $(function () {
                $('#colors_sketch').sketch();
                $(".tools a").eq(0).attr("style", "color:#000");
                $(".tools a").click(function () {
                    $(".tools a").removeAttr("style");
                    $(this).attr("style", "color:#000");
                });
                $("#btnSave").bind("click", function () {                 
                    var base64 = $('#colors_sketch')[0].toDataURL();
                    $('[Id*=ImageVal]').val(base64);
                });
            });
        </script>
    </div>
</form>

C#

private string contring = ConfigurationManager.ConnectionStrings["Constring"].ToString();

protected void Page_Load(Object sender, EventArgs e)
{
    if (!this.IsPostBack)
    {
        GetData();
    }
}
protected void OnUpload(Object sender, EventArgs e)
{
    byte[] bytes = Convert.FromBase64String(ImageVal.Value.Split(',')[1]);
    using (FileStream stream = new FileStream(Server.MapPath("~/Images/" + txtImageName.Text.Trim() + ".png"), FileMode.Create))
    {
        stream.Write(bytes, 0, bytes.Length);
        stream.Flush();
    }

    using (SqlConnection con = new SqlConnection(contring))
    {
        using (SqlCommand cmd = new SqlCommand("INSERT INTO [File](FileName) VALUES(@ImageName)", con))
        {
            cmd.Parameters.AddWithValue("@ImageName", "Images/" + txtImageName.Text.Trim() + ".png");
            using (SqlDataAdapter sda = new SqlDataAdapter(cmd))
            {
                DataTable dt = new DataTable();
                sda.Fill(dt);
            }
        }
    }
    txtImageName.Text = "";
    this.GetData();
}

private void GetData()
{
    using (SqlConnection con = new SqlConnection(contring))
    {
        using (SqlCommand cmd = new SqlCommand("SELECT [FileName] FROM [File]", con))
        {
            using (SqlDataAdapter sda = new SqlDataAdapter(cmd))
            {
                DataTable dt = new DataTable();
                sda.Fill(dt);
                GvImage.DataSource = dt;
                GvImage.DataBind();
            }
        }
    }
}

VB.Net

Private contring As String = ConfigurationManager.ConnectionStrings("Constring").ToString()

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

Protected Sub OnUpload(sender As [Object], e As EventArgs)
    Dim bytes As Byte() = Convert.FromBase64String(ImageVal.Value.Split(","c)(1))
    Using stream As New FileStream(Server.MapPath("~/Images/" + txtImageName.Text.Trim() + ".png"), FileMode.Create)
        stream.Write(bytes, 0, bytes.Length)
        stream.Flush()
    End Using

    Using con As New SqlConnection(contring)
        Using cmd As New SqlCommand("INSERT INTO [File](FileName) VALUES(@FileName)", con)
            cmd.Parameters.AddWithValue("@FileName", "Images/" + txtImageName.Text.Trim() + ".png")
            Using da As New SqlDataAdapter(cmd)
                Dim dt As New DataTable()
                da.Fill(dt)
            End Using
        End Using
    End Using
    txtImageName.Text = ""
    Me.GetData()
End Sub

Private Sub GetData()
    Using con As New SqlConnection(contring)
        Using cmd As New SqlCommand("SELECT [FileName] FROM [File]", con)
            Using sda As New SqlDataAdapter(cmd)
                Dim dt As New DataTable()
                sda.Fill(dt)
                GvImage.DataSource = dt
                GvImage.DataBind()
            End Using
        End Using
    End Using
End Sub

Screenshot