想要gridview只填写按钮点击

所以我一直在asp.net中使用一个sqldatasource与多个控制参数的搜索工作。如果一个控件被填充，而另一个控件没有(如果我留下一个空白，它不会带来任何东西)，我花了一点时间来搜索我的表。我现在唯一的问题是，一旦页面打开，它将填写整个数据库的网格视图。也许我去这一切都错了，但我的最终意图是有一个搜索页面与8个文本框通过数据库搜索。任何帮助都将非常感激。我不确定这是不是你需要的全部信息，但请告诉我。提前感谢大家。

<asp:SqlDataSource ID="SqlDataSource4" runat="server" ConnectionString="<%$ ConnectionStrings:Conn %>" CancelSelectOnNullParameter="false"
    SelectCommand="SELECT [ID], [ContractNo], [OMBEmp], [Cono], [ReviewDate], [AmendNo], [RType], [Contractor], [Purpose], [Department] FROM [tblContractLog] WHERE (([ContractNo] = @ContractNo OR @ContractNo = '') AND ([OMBEmp] = @OMBEmp OR @OMBEmp = '') AND ([Cono] = @Cono OR @Cono = '') AND ([AmendNo] = @AmendNo OR @AmendNo = '') AND ([RType] = @RType OR @RType = '') AND ([Contractor] = @Contractor OR @Contractor = '') AND ([Purpose] = @Purpose OR @Purpose = '') AND ([Department] = @Department OR @Department = ''))">
        <SelectParameters>
            <asp:ControlParameter ControlID="contractnumb" Name="ContractNo" 
                PropertyName="Text" Type="String" ConvertEmptyStringToNull="false"/>
            <asp:ControlParameter ControlID="employeetext" Name="OMBEmp" 
                PropertyName="Text" Type="String" ConvertEmptyStringToNull="false"/>
            <asp:ControlParameter ControlID="conumb" Name="Cono" 
                PropertyName="Text" Type="String" ConvertEmptyStringToNull="false"/>
                <asp:ControlParameter ControlID="amendnumbtxt" Name="AmendNo" 
                PropertyName="Text" Type="String" ConvertEmptyStringToNull="false"/>
            <asp:ControlParameter ControlID="rtypetxt" Name="RType" 
                PropertyName="Text" Type="String" ConvertEmptyStringToNull="false"/>
            <asp:ControlParameter ControlID="contractortxt" Name="Contractor" 
                PropertyName="Text" Type="String" ConvertEmptyStringToNull="false"/>
            <asp:ControlParameter ControlID="purposetxt" Name="Purpose" 
                PropertyName="Text" Type="String" ConvertEmptyStringToNull="false"/>
            <asp:ControlParameter ControlID="departmenttxt" Name="Department" 
                PropertyName="Text" Type="String" ConvertEmptyStringToNull="false"/>
        </SelectParameters>
    </asp:SqlDataSource>

protected void SqlDataSource1_Selecting(object sender, SqlDataSourceSelectingEventArgs e)
{
    if (!IsPostBack)
        e.Cancel = true;
}