How to get the DataKey value in RowDataBound event for GridView

Please try with following code.

protected void GridView3_RowDataBound(object sender, GridViewRowEventArgs e)
    {
        if (e.Row.RowType == DataControlRowType.DataRow)
        {
            string lsDataKeyValue = GridView3.DataKeys[e.Row.RowIndex].Values[0].ToString();
        }
    }

How to Get DataKey value of a Row in RowDataBound or RowCommand Event in ASP.Net GridView control ?

We will normally set the primary key field to the DataKeyNames property of GridView control to identify the row. This little code snippet will help us to find the data keys assocciated with a row in DataBound and RowCommand event in codebehind file.

Refer the below code,
ASPX
  <asp:GridView ID="gvUsers" runat="server" AutoGenerateColumns="False"
            DataKeyNames="UserID" OnRowDataBound="gvUsers_RowDataBound"
            RowStyle-CssClass="Row" onrowcommand="gvUsers_RowCommand">
                    <Columns>                     
                        <asp:BoundField DataField="FirstName" HeaderText="First Name" ReadOnly="True" />
                        <asp:BoundField DataField="LastName" HeaderText="Last Name" ReadOnly="True" />    
                         <asp:BoundField DataField="Email" HeaderText="Email" ReadOnly="True" />
                         <asp:TemplateField>
                         <ItemTemplate>
                        <asp:Button runat="server" Text="SELECT" CommandName="Select" />                            
                        </ItemTemplate>
                         </asp:TemplateField>                      
                    </Columns>                  
                    <HeaderStyle BackColor="#F06300" Font-Bold="True" ForeColor="#FFFFCC" />
     </asp:GridView>

RowDataBound Event
protected void gvUsers_RowDataBound(object sender, GridViewRowEventArgs e)
    {      
        if (e.Row.RowType == DataControlRowType.DataRow)
        {
            object objTemp = gvUsers.DataKeys[e.Row.RowIndex].Value as object;
            if (objTemp != null)
            {
                string id = objTemp.ToString(); //Do your operations
            }
         
        }
    }

RowCommand Event
    protected void gvUsers_RowCommand(object sender, GridViewCommandEventArgs e)
    {
      Control ctl = e.CommandSource as Control;
      GridViewRow CurrentRow = ctl.NamingContainer as GridViewRow;
      object objTemp = gvUsers.DataKeys[CurrentRow.RowIndex].Value as object;
      if (objTemp != null)
      {
          string id = objTemp.ToString(); //Do your operations
      }
    }

call a JQuery function from code behind in C#

I want to call this JQuery function from C# code behind

ScriptManager.RegisterStartupScript(this.Page, this.GetType(), "myfunction", "myFunction(params...);", true);