不能在表中插入外键

我试图插入外键到表与DropDownList，它看起来很好，但是当我按下添加按钮时出现了这个错误

" mysql.data.mysqlclient。你的SQL有一个错误语法;检查MySQL服务器版本对应的手册为了正确的语法使用near ')值(1,1,1,1)' at line 1"}

表有另一个变量，但现在他们不重要，他们的默认值是null。

我没有足够的信誉来添加图像与表之间的关系。

谢谢! !

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data;
using MySql.Data.MySqlClient;

namespace WebApplication1
{
    public partial class usageDisp : System.Web.UI.Page
    {
        string connectionstring = @"Data Source=localhost; Database=globaldotdb; user ID=root; Password=peleg1708";
        protected void Page_Load(object sender, EventArgs e)
        {
            if (!IsPostBack)
            {
                //check
                BindData();
            }
        }
        private void BindData()
        {         
            using (MySqlConnection cn = new MySqlConnection(connectionstring))
            {
                MySqlDataAdapter adp = new MySqlDataAdapter(("SELECT  tblusage.codeUsage,tblcustom.Customer, tblvendor.Vendor, tblusage.dateStart, tblusage.dateEnd, tblregion.Region, tblservice.Service, tblservice.unit, tblusage.isSecure,tblusage.Usage FROM     ((((tblvendor INNER JOIN tblusage ON tblvendor.codeVendor = tblusage.codeVendor) INNER JOIN  tblservice ON tblusage.codeService = tblservice.codeService) INNER JOIN  tblregion ON tblusage.codeRegion = tblregion.codeRegion) INNER JOIN  tblcustom ON tblusage.codeCust = tblcustom.codeCust)"), cn);
                DataTable dt = new DataTable();
                adp.Fill(dt);
                if (dt.Rows.Count > 0)
                {
                    gv.DataSource = dt;
                    gv.DataBind();

                }
            }
        }
        protected void gv_RowDeleting(object sender, GridViewDeleteEventArgs e)
        {
            int codeusage = int.Parse(gv.DataKeys[e.RowIndex].Value.ToString());
            deleteusage(codeusage);
            BindData();
        }
        private void deleteusage(int codeusage)
        {
            using (MySqlConnection cn = new MySqlConnection(connectionstring))
            {
                string query = "DELETE FROM tblusage WHERE codeUsage=" + codeusage + " ";
                MySqlCommand cmd = new MySqlCommand(query, cn);
                cn.Open();
                cmd.ExecuteNonQuery();
            }
        }
        protected void gv_DataBound(object sender, EventArgs e)
        {
            DropDownList DDLCu = gv.FooterRow.FindControl("DDLCu") as DropDownList;
            DropDownList DDLVe = gv.FooterRow.FindControl("DDLVe") as DropDownList;
            DropDownList DDLSe = gv.FooterRow.FindControl("DDLSe") as DropDownList;
            DropDownList DDLRe = gv.FooterRow.FindControl("DDLRe") as DropDownList;

            using (MySqlConnection cn = new MySqlConnection(connectionstring))
            {
                MySqlDataAdapter Cadp = new MySqlDataAdapter(("SELECT * from tblcustom"), cn);
                DataTable Cdt = new DataTable();
                Cadp.Fill(Cdt);
                if (Cdt.Rows.Count > 0)
                {
                    DDLCu.DataSource = Cdt;
                    DDLCu.DataTextField = "Customer";
                    DDLCu.DataValueField = "codeCust";
                    DDLCu.DataBind();
                }

                MySqlDataAdapter Vadp = new MySqlDataAdapter(("SELECT * from tblvendor"), cn);
                DataTable Vdt = new DataTable();
                Vadp.Fill(Vdt);
                if (Vdt.Rows.Count > 0)
                {
                    DDLVe.DataSource = Vdt;
                    DDLVe.DataTextField = "Vendor";
                    DDLVe.DataValueField = "codeVendor";
                    DDLVe.DataBind();
                }

                MySqlDataAdapter Sadp = new MySqlDataAdapter(("SELECT * from tblservice"), cn);
                DataTable Sdt = new DataTable();
                Sadp.Fill(Sdt);
                if (Sdt.Rows.Count > 0)
                {
                    DDLSe.DataSource = Sdt;
                    DDLSe.DataTextField = "Service";
                    DDLSe.DataValueField = "codeService";
                    DDLSe.DataBind();
                }

                MySqlDataAdapter Radp = new MySqlDataAdapter(("SELECT * from tblregion"), cn);
                DataTable Rdt = new DataTable();
                Radp.Fill(Rdt);
                if (Rdt.Rows.Count > 0)
                {
                    DDLRe.DataSource = Rdt;
                    DDLRe.DataTextField = "Region";
                    DDLRe.DataValueField = "codeRegion";
                    DDLRe.DataBind();
                }
            }
        }
        protected void lnkAdd_Click(object sender, EventArgs e)
        {
            DropDownList DDLCu = gv.FooterRow.FindControl("DDLCu") as DropDownList;
            DropDownList DDLVe = gv.FooterRow.FindControl("DDLVe") as DropDownList;
            DropDownList DDLSe = gv.FooterRow.FindControl("DDLSe") as DropDownList;
            DropDownList DDLRe = gv.FooterRow.FindControl("DDLRe") as DropDownList;
            int cc = int.Parse(DDLCu.SelectedValue);
            int cv = int.Parse(DDLVe.SelectedValue);
            int cs = int.Parse(DDLSe.SelectedValue);
            int cr = int.Parse(DDLRe.SelectedValue);
            add(cc, cv, cs, cr );
            BindData();
            Response.Redirect("http://localhost:56717/usage.aspx");
        }
        private void add(int cc, int cv,  int cs, int cr)
        {
            using (MySqlConnection cn = new MySqlConnection(connectionstring))
            {
                string query = "insert into tblusage(codeCust,codeVendor,codeService,codeRegion,) values (" + cc + "," + cv +"," + cs + "," + cr  + ") ";
                MySqlCommand cmd = new MySqlCommand(query, cn);
                cn.Open();
                cmd.ExecuteNonQuery();
            }
        }


    }
}

<asp:GridView ID="gv" runat="server" 
    DataKeyNames="codeUsage" 
        onrowdeleting="gv_RowDeleting" 
         AutoGenerateColumns="False" ondatabound="gv_DataBound" ShowFooter="True">
    <Columns>
        <asp:TemplateField HeaderText="codeusage" Visible="False">
            <EditItemTemplate>
                <asp:TextBox ID="txtcode" runat="server" Text='<%# Eval("codeUsage") %>'></asp:TextBox>
            </EditItemTemplate>
            <ItemTemplate>
                <asp:Label ID="Label1" runat="server" Text='<%# Eval("codeUsage") %>'></asp:Label>
            </ItemTemplate>
        </asp:TemplateField>
        <asp:TemplateField HeaderText="Customer">
            <EditItemTemplate>
                <asp:TextBox ID="TXTCust" runat="server" Text='<%# Eval("Customer") %>'></asp:TextBox>
            </EditItemTemplate>
            <FooterTemplate>
                <asp:DropDownList ID="DDLCu" runat="server" AutoPostBack="True">
                </asp:DropDownList>
            </FooterTemplate>
            <ItemTemplate>
                <asp:Label ID="Label2" runat="server" Text='<%# Eval("Customer") %>'></asp:Label>
            </ItemTemplate>
        </asp:TemplateField>
        <asp:TemplateField HeaderText="Vendor">
            <EditItemTemplate>
                <asp:TextBox ID="TextBox1" runat="server" Text='<%# Eval("Vendor") %>'></asp:TextBox>
            </EditItemTemplate>
            <FooterTemplate>
                <asp:DropDownList ID="DDLVe" runat="server" AutoPostBack="True">
                </asp:DropDownList>
            </FooterTemplate>
            <ItemTemplate>
                <asp:Label ID="Label3" runat="server" Text='<%# Eval("Vendor") %>'></asp:Label>
            </ItemTemplate>
        </asp:TemplateField>
        <asp:TemplateField HeaderText="dateStart">
            <EditItemTemplate>
                <asp:TextBox ID="TXTDS" runat="server" Text='<%# Eval("dateStart") %>'></asp:TextBox>
            </EditItemTemplate>
            <ItemTemplate>
                <asp:Label ID="Label4" runat="server" Text='<%# Eval("dateStart") %>'></asp:Label>
            </ItemTemplate>
        </asp:TemplateField>
        <asp:TemplateField HeaderText="dateEnd">
            <EditItemTemplate>
                <asp:TextBox ID="TXTDE" runat="server" Text='<%# Eval("dateEnd") %>'></asp:TextBox>
            </EditItemTemplate>
            <ItemTemplate>
                <asp:Label ID="Label5" runat="server" Text='<%# Eval("dateEnd") %>'></asp:Label>
            </ItemTemplate>
        </asp:TemplateField>
        <asp:TemplateField HeaderText="service">
            <EditItemTemplate>
                <asp:TextBox ID="TXTSe" runat="server" Text='<%# Eval("Service") %>'></asp:TextBox>
            </EditItemTemplate>
            <FooterTemplate>
                <asp:DropDownList ID="DDLSe" runat="server" AutoPostBack="True">
                </asp:DropDownList>
            </FooterTemplate>
            <ItemTemplate>
                <asp:Label ID="Label6" runat="server" Text='<%# Eval("Service") %>'></asp:Label>
            </ItemTemplate>
        </asp:TemplateField>
        <asp:TemplateField HeaderText="region">
            <EditItemTemplate>
                <asp:TextBox ID="TXTRe" runat="server" Text='<%# Eval("Region") %>'></asp:TextBox>
            </EditItemTemplate>
            <FooterTemplate>
                <asp:DropDownList ID="DDLRe" runat="server" AutoPostBack="True">
                </asp:DropDownList>
            </FooterTemplate>
            <ItemTemplate>
                <asp:Label ID="Label7" runat="server" Text='<%# Eval("Region") %>'></asp:Label>
            </ItemTemplate>
        </asp:TemplateField>
        <asp:TemplateField HeaderText="isSecure">
            <EditItemTemplate>
                <asp:TextBox ID="TXTIS" runat="server" Text='<%# Eval("isSecure") %>'></asp:TextBox>
            </EditItemTemplate>
            <ItemTemplate>
                <asp:Label ID="Label8" runat="server" Text='<%# Eval("isSecure") %>'></asp:Label>
            </ItemTemplate>
        </asp:TemplateField>
        <asp:TemplateField HeaderText="unit">
            <EditItemTemplate>
                <asp:TextBox ID="TXTunit" runat="server" Text='<%# Eval("unit") %>'></asp:TextBox>
            </EditItemTemplate>
            <ItemTemplate>
                <asp:Label ID="Label9" runat="server" Text='<%# Eval("unit") %>'></asp:Label>
            </ItemTemplate>
        </asp:TemplateField>
        <asp:TemplateField HeaderText="usage">
            <EditItemTemplate>
                <asp:TextBox ID="TXTusage" runat="server" Text='<%# Eval("Usage") %>'></asp:TextBox>
            </EditItemTemplate>
            <FooterTemplate>
                <asp:LinkButton ID="lnkAdd" runat="server" onclick="lnkAdd_Click">add</asp:LinkButton>
            </FooterTemplate>
            <ItemTemplate>
                <asp:Label ID="Label10" runat="server" Text='<%# Eval("Usage") %>'></asp:Label>
            </ItemTemplate>
        </asp:TemplateField>
        <asp:CommandField HeaderText="Operation" ShowDeleteButton="True" />
    </Columns>
</asp:GridView>