Decimal datatype parameter to EntityDataSource.

Trying to add decimal datatype parameter to  EntityDataSource.
 is not working (not filtering results ), not raising error.

Code :
   plu_parametrs += "it.Plu_L_Store=@store_num";
                PLUEntityDataSource.WhereParameters.Add("store_num", TypeCode.Int32,        StoreDropDown.SelectedValue.ToString());

 plu_parametrs += "it.Plu_L_Dept=@dept_id";
  PLUEntityDataSource.WhereParameters.Add("dept_id", TypeCode.Int32, DropDownDept.SelectedValue.ToString());

                plu_parametrs += "it.Plu_L_plu=@txtsearch";
                PLUEntityDataSource.WhereParameters.Add("txtsearch", TypeCode.Decimal, txtsearch.Text);

            PLUEntityDataSource.Where = plu_parametrs.ToString();
            PLUEntityDataSource.DataBind();

ASPX code :

 <asp:EntityDataSource ID="PLUEntityDataSource" runat="server"
        ConnectionString="name=GSEntities"
        EnableFlattening="False" EnableInsert="True" EnableUpdate="True"
        EntitySetName="plulookups"
        Where="it.Plu_L_Store=@store_num and it.Plu_L_Dept=@dept_id and it.Plu_L_Margin = @Plu_L_Price" DefaultContainerName="GSEntities" >
        <WhereParameters>
            <asp:ControlParameter ControlID="StoreDropDown" Name="store_num"
                PropertyName="SelectedValue" Type="Int32" />
            <asp:ControlParameter Name="dept_id" Type="Int32" ControlID="DropDownDept"
                PropertyName="SelectedValue" />
            <asp:ControlParameter Name="Plu_L_Price" DefaultValue="100" DbType ="Decimal" ControlID="txtprice" PropertyName="Text"/>
        </WhereParameters>
    </asp:EntityDataSource>
            GridView1.DataBind();