Autogenerated Gridview with All Cells in Edit Mode by Default - asp.net

Question

So I've got a gridview bound to a SQL datasource stored procedure. The stored procedure returns a pivot table, where a number of columns are unknown until run time. I therefore need to autogenerate the columns.
The gridview is intended to allow Excel-like data updates. So the goal is to have the grid load as textboxes. I know if I were to declare the columns on my aspx page, I could create template columns and handle their visibility that way.
So I believe I need a way to programmatically set all the columns to template fields (without knowing the column names), or I need to discover the method by which I can just "flip the switch" and just make everything editable.
Thanks in advance!
<asp:GridView ID="GridView1" runat="server" DataSourceID="SqlDataSourceExcelGridTest">
</asp:GridView>
<asp:SqlDataSource ID="SqlDataSourceExcelGridTest" runat="server" ConnectionString="<%$ ConnectionStrings:WebAppsConnectionString %>" SelectCommand="spJobForecastingGetEmployeesByDepartmentAndProject_v1" SelectCommandType="StoredProcedure" UpdateCommand="spJobForecastingUpdateHours" UpdateCommandType="StoredProcedure">
<SelectParameters>
<asp:Parameter Name="DepartmentNumber" Type="String" DefaultValue="13211" />
<asp:Parameter Name="ProjectNumber" Type="String" DefaultValue="13211" />
<asp:Parameter Name="startDate" Type="DateTime" DefaultValue="2/21/2014" />
</SelectParameters>
<UpdateParameters>
<asp:Parameter Name="DepartmentNumber" Type="String" />
<asp:Parameter Name="ProjectNumber" Type="String" />
<asp:Parameter Name="Alias" Type="String" />
<asp:Parameter Name="WorkWeek" Type="DateTime" />
<asp:Parameter Name="WorkHours" Type="Int32" />
</UpdateParameters>
</asp:SqlDataSource>

Answer 1

try this:
UPDATED CODE
<asp:GridView ID="GridView1" runat="server" DataSourceID="SqlDataSourceExcelGridTest">
</asp:GridView>
<asp:SqlDataSource ID="SqlDataSourceExcelGridTest" runat="server" ConnectionString="<%$ ConnectionStrings:WebAppsConnectionString %>" SelectCommand="spJobForecastingGetEmployeesByDepartmentAndProject_v1" SelectCommandType="StoredProcedure" UpdateCommand="spJobForecastingUpdateHours" UpdateCommandType="StoredProcedure">
<SelectParameters>
<asp:Textbox ID="DepartmentNumber" DefaultValue="13211" text='<%# Eval("DepartmentNumber") %>'></asp:TextBox>
<asp:Textbox ID="ProjectNumber" Type="String" DefaultValue="13211" Text='<%# Eval("ProjectNumber") %>'></asp:TextBox>
<asp:Textbox ID="startDate" Type="DateTime" DefaultValue="2/21/2014" Text='<%# Eval("startDate") %>'></asp:TextBox>
</SelectParameters>
<UpdateParameters>
<asp:Textbox ID="DepartmentNumber" Type="String" text='<%# Eval("DepartmentNumber") %>'></asp:TextBox>
<asp:Textbox ID="ProjectNumber" Type="String" text='<%# Eval("ProjectNumber") %>'></asp:TextBox>
<asp:Textbox ID="Alias" Type="String" text='<%# Eval("Alias") %>'></asp:TextBox>
<asp:Textbox ID="WorkWeek" Type="DateTime" text='<%# Eval("WorkWeek") %>'></asp:TextBox>
<asp:Textbox ID="WorkHours" Type="Int32" text='<%# Eval("WorkHours") %>'></asp:TextBox>
</UpdateParameters>
</asp:SqlDataSource>