How to pass a variable to the SelectCommand of a SqlDataSource?

Try this instead, remove the SelectCommand property and SelectParameters:

<asp:SqlDataSource ID="SqlDataSource1" runat="server"     ConnectionString="<%$ ConnectionStrings:itematConnectionString %>">

Then in the code behind do this:

SqlDataSource1.SelectParameters.Add("userId", userId.ToString());SqlDataSource1.SelectCommand = "SELECT items.name, items.id FROM items INNER JOIN users_items ON items.id = users_items.id WHERE (users_items.user_id = @userId) ORDER BY users_items.date DESC"

While this worked for me, the following code also works:

<asp:SqlDataSource ID="SqlDataSource1" runat="server"     ConnectionString="<%$ ConnectionStrings:itematConnectionString %>"    SelectCommand = "SELECT items.name, items.id FROM items INNER JOIN users_items ON items.id = users_items.id WHERE (users_items.user_id = @userId) ORDER BY users_items.date DESC"></asp:SqlDataSource>SqlDataSource1.SelectParameters.Add("userid", DbType.Guid, userId.ToString());

we had to do this so often that I made what I called a DelegateParameter class

using System;using System.Collections.Generic;using System.Text;using System.Web.UI.WebControls;using System.Reflection;namespace MyControls{    public delegate object EvaluateParameterEventHandler(object sender, EventArgs e);    public class DelegateParameter : Parameter    {        private System.Web.UI.Control _parent;        public System.Web.UI.Control Parent        {            get { return _parent; }            set { _parent = value; }        }        private event EvaluateParameterEventHandler _evaluateParameter;        public event EvaluateParameterEventHandler EvaluateParameter        {            add { _evaluateParameter += value; }            remove { _evaluateParameter -= value; }        }        protected override object Evaluate(System.Web.HttpContext context, System.Web.UI.Control control)        {            return _evaluateParameter(this, EventArgs.Empty);        }    }}

put this class either in your app_code (remove the namespace if you put it there) or in your custom control assembly. After the control is registered in the web.config you should be able to do this

<asp:SqlDataSource ID="SqlDataSource1" runat="server"     ConnectionString="<%$ ConnectionStrings:itematConnectionString %>"    SelectCommand = "SELECT items.name, items.id FROM items INNER JOIN users_items ON items.id = users_items.id WHERE (users_items.user_id = @userId) ORDER BY users_items.date DESC">    <SelectParameters>    <asp:DelegateParameter Name="userId"  DbType="Guid" OnEvaluate="GetUserID" />    </SelectParameters></asp:SqlDataSource>

then in the code behind you implement the GetUserID anyway you like.

protected object GetUserID(object sender, EventArgs e){  return userId;}

Just add a custom property to the page which will return the variable of your choice. You can then use the built-in "control" parameter type.

In the code behind, add:

Dim MyVariable as LongReadOnly Property MyCustomProperty As Long    Get        Return MyVariable    End GetEnd Property

In the select parameters section add:

<asp:ControlParameter ControlID="__Page" Name="MyParameter" PropertyName="MyCustomProperty" Type="Int32" />