C＃检查返回数据表

Question

I need check return datatable and count rows in my asp net GridView code.

I tried this solution, I don't have error but the code not showing the alert and not count the rows.

My code below.

I would greatly appreciate any help you can give me in working this problem.

public DataTable GridViewBind()
{
    sql = " SELECT * FROM tbl; ";

    try
    {
        dadapter = new OdbcDataAdapter(sql, conn);
        dset = new DataSet();
        dset.Clear();
        dadapter.Fill(dset);
        DataTable dt = dset.Tables[0];
        GridView1.DataSource = dt;
        GridView1.DataBind();
        return dt;

        if (dt.Rows.Count == 0)
        {
            Page.ClientScript.RegisterStartupScript(this.GetType(), "Alert", "alert('No data.');window.location='default.aspx';", true);
        }
    }
    catch (Exception ex)
    {
        throw ex;
    }
    finally
    {
        dadapter.Dispose();
        dadapter = null;
        conn.Close();
    }
}

Answer 1

Of course the code isn't showing the alert. You're returning from the method before that happens:

return dt;
// nothing after this will execute
if (dt.Rows.Count == 0)
{
    Page.ClientScript.RegisterStartupScript(this.GetType(), "Alert", "alert('No data.');window.location='default.aspx';", true);
}

The compiler should be warning you about this. Don't ignore compiler warnings.

You can simply move your return statement to the end of the code block:

if (dt.Rows.Count == 0)
{
    Page.ClientScript.RegisterStartupScript(this.GetType(), "Alert", "alert('No data.');window.location='default.aspx';", true);
}
return dt;

Side-note: Your catch block is:

1. Throwing away meaningful stack trace information
2. Entirely superfluous

Just remove the catch block entirely and keep the try and finally . If you ever do need to re-throw an exception from a catch block, just use the command:

throw;

This preserves the original exception, instead of replacing it with a new similar one.