In this article I will explain with an example and attached sample code, how to pass Text (Value) of TextBox as CommandParameter to SqlDataSource in ASP.Net.
Here I am making use of Microsoft’s Northwind Database. You can download it from here
Populating and Filtering the GridView
In the HTML Markup, there is an ASP.Net GridView control, a TextBox and a Button.
The GridView with records from the Customers table of the Northwind database using SqlDataSource. For the SqlDataSource, I have specified FilterExpression along with the SelectCommand, using which the records are filtered based on the value entered in the TextBox using LIKE statement
Search Customer:
<asp:TextBox ID="txtSearch" runat="server"></asp:TextBox>
<asp:Button ID="btnSearch" runat="server" Text="Search" />
<hr />
<asp:GridView ID="GridView1" HeaderStyle-BackColor="#3AC0F2" HeaderStyle-ForeColor="White"
    runat="server" AutoGenerateColumns="false" DataSourceID="GridDataSource" AllowPaging="true">
        <asp:BoundField DataField="ContactName" HeaderText="Name" ItemStyle-Width="150" />
        <asp:BoundField DataField="City" HeaderText="City" ItemStyle-Width="150" />
        <asp:BoundField DataField="Country" HeaderText="Country" ItemStyle-Width="150" />
<asp:SqlDataSource ID="GridDataSource" runat="server" ConnectionString="<%$ ConnectionStrings:ConStr %>"
    SelectCommand="SELECT ContactName, City, Country FROM Customers" FilterExpression="ContactName LIKE '{0}%'">
        <asp:ControlParameter Name="Country" ControlID="txtSearch" PropertyName="Text" />
SelectCommand – Here we need to set the default SQL Query without any WHERE Clause or filter.
FilterExpression – Here we need to set the filter part of the SQL Query with a placeholder {0}. The placeholder {0} will be replaced by the value of the ControlParameter, i.e. the TextBox’s Text
FilterParameters – Here we specify the Control Parameters to be used by the FilterExpression
As soon as some text is entered in the TextBox and the Search Button is clicked, the GridView records are filtered.
Note: SqlDataSource can also filter records in GridView using QueryString Parameters, to know more about it please refer ASP.Net SqlDataSource pass value to SelectParameter using QueryString Parameter Example
Pass TextBox Text (Value) as Parameter to SqlDataSource in ASP.Net

Pass TextBox Text (Value) as Parameter to SqlDataSource in ASP.Net