How to pass external values with GridView HyperLinkField which are not part of your Gridview DataSource member

Few days ago, I published an article “How to pass multiple values using GridView HyperLinkField?”, where I explained how you can pass multiple parameters with Gridview HyperLinkField using DataNavigationUrlField and DataNavigateUrlFormatString properties. In this post, I am going to explain how you can pass some external values as parameters with the same hyperlink field.

DataNavigationUrlField uses only those fields as parameter which are part of GridView DataSource. Now the problem comes when you want to pass some other variables as parameters which are not part of the DataSource. As shown in the image below, we are passing EmpID and ParentId as arguments and these two field are the data members of GridView DataSource.

Now say, You want to pass ChildID for that particular record along with ParentID and EmpID and you want that the hyperlink URL should be like “Default.aspx?EmpID=1&ParentID=P1&ChildID=C1”where ChildID is not part of datasource.

You can achieve this by writing code in code behind for the particular GridView. There are two events where you can overwrite the navigation URL of that hyperlink field. You can use Gridview_RowDataBound or Gridview_PreRender for the same.

Let’s start with Gridview_RowDataBound. The RowDataBound event of GridView is raised when a data row is bound to data. So for each and every row RowDataBound event is raised to bind with actual data from the data source. On the RowDataBound event, you can check for the particular Cell control and can append the NavigateURL. Below is the code snippet for the same:

/// <summary>
/// Handles the RowDataBound event of the grdStudent control.
/// </summary>
/// <param name="sender">The source of the event.</param>
/// <param name="e">The <see cref="System.Web.UI.WebControls.GridViewRowEventArgs"/> 
/// instance containing the event data.</param>
protected void grdStudent_RowDataBound(object sender, GridViewRowEventArgs e)
{
    if (e.Row.RowType == DataControlRowType.DataRow)
    {
        HyperLink hyperlink = (HyperLink)e.Row.Cells[0].Controls[0];
        hyperlink.NavigateUrl += "&ChildID=" + this.ExternalValue;
    }
} 

And you can do the same thing in Gridview_PreRender event in a similar way. As per the ASP.NET page life cycle, Pre_Render for control is raised just before save view state and Render event. So this is the last event where you can customize your control before saving the viewstate data and rendering it. Below is the code snippet for the same:

/// <summary>
/// Handles the PreRender event of the grdStudent control.
/// </summary>
/// <param name="sender">The source of the event.</param>
/// <param name="e">The <see cref="System.EventArgs"/> 
/// instance containing the event data.</param>
protected void grdStudent_PreRender(object sender, EventArgs e)
{
    foreach (GridViewRow row in grdStudent.Rows)
    {
        if (row.RowType == DataControlRowType.DataRow)
        {
             HyperLink grdviewLink = (HyperLink)row.Cells[0].Controls[0];
             grdviewLink.NavigateUrl += "&ChildID=" + this.externalValue;
        }
    }
}

If you want to know how it’s actually working, just set a breakpoint during databound, you will find NavigateURL for that hyperlink field has already been set with the value that you have passed as DataNavigationUrlField. And inside RowDataBound or Pre_Render, we are appending the same NavigateURL with an external parameter.

Below is the HTML snippet for the same HyperLinkField.

You can use NavigateURL properties for Hyperlinkfield to set URL, but NavigateURL will set the same URL for all the rows. So if you want a different URL for each and every row, you have to use DataNavigationUrlField or you need to override the NavigateURL during RowDataBound or Pre_Render. And if you set both the properties (NavigateURL and DataNavigationUrlField) the DataNavigationUrlField property takes precedence.

I hope this post will help you.

Filed under: ASP.NET, Tips and Tricks, Visual Studio