Convert textbox in gridview to accept value that are of datetime and deimal into database

Question

Hi, I have try convert sqldatetime and decimal datatype to string such that the textbox is able to enter datetime value.But there is an error.
This is my code:

 

protected void 
gvContract_RowUpdating(object sender, GridViewUpdateEventArgs e)

{

DateTime startDate = Convert.ToDateTime(gvContract.DataKeys[e.RowIndex].Value.ToString());

DateTime endDate = Convert.ToDateTime(gvContract.DataKeys[e.RowIndex].Value.ToString());

decimal amount = Convert.ToDecimal(gvContract.DataKeys[e.RowIndex].Value.ToString());



Label txtContractID = (Label)gvContract.Rows[e.RowIndex].FindControl("txtContractID");

TextBox txtEmpName = (TextBox)gvContract.Rows[e.RowIndex].FindControl("txtEmpName");

TextBox txtStartDate = (TextBox)gvContract.Rows[e.RowIndex].FindControl("txtStartDate");

TextBox txtEndDate = (TextBox)gvContract.Rows[e.RowIndex].FindControl("txtEndDate");

TextBox txtAmount = (TextBox)gvContract.Rows[e.RowIndex].FindControl("txtAmount");

TextBox txtVendorBrn = (TextBox)gvContract.Rows[e.RowIndex].FindControl("txtVendorBrn");

TextBox txtName = (TextBox)gvContract.Rows[e.RowIndex].FindControl("txtName ");

TextBox txtProducts = (TextBox)gvContract.Rows[e.RowIndex].FindControl("txtProducts ");

TextBox txtRef = (TextBox)gvContract.Rows[e.RowIndex].FindControl("txtRef");

TextBox txtProj = (TextBox)gvContract.Rows[e.RowIndex].FindControl("txtPro ");

TextBox txtAlert = (TextBox)gvContract.Rows[e.RowIndex].FindControl("txtAlert");

TextBox txtTemplateID = (TextBox)gvContract.Rows[e.RowIndex].FindControl("txtTemplateID ");



vrmdb.Update_ContractRecords(txtContractID.Text, 
txtEmpName.Text,txtStartDate.Text, txtEndDate.Text, 
txtAmount.Text,txtVendorBrn.Text,txtName.Text,txtProducts.Text,txtRef.Text, 
txtProj.Text,txtAlert.Text,txtTemplateID.Text);

gvContract.EditIndex = -1;

BindGrid(true);

Response.Redirect("ContractManagement.aspx");

}

}

}

May I know how to convert the textbox such that they are able to accpet value that are of datetime and decimal. Thks!