C# 条件表达式中的数据类型不匹配错误（ms Access）

请找出我代码中的错误。它显示

条件表达式中的数据类型不匹配错误

一定是这样

OleDbCommand cmd = new OleDbCommand(
                "DELETE tbbill.*, tbgrid.* 
                 FROM tbbill 
                 INNER JOIN tbgrid 
                    ON tbbill.invoice = tbgrid.ginovice 
                 WHERE tbbill.invoice = " + Convert.ToInt32(txtinvoice.Text) , con);

我已从发票中删除

'

然而，您应该始终使用参数化SQL来防止SQL注入

OleDbCommand cmd = new OleDbCommand(
                "DELETE tbbill.*, tbgrid.* 
                 FROM tbbill 
                 INNER JOIN tbgrid 
                    ON tbbill.invoice = tbgrid.ginovice 
                 WHERE tbbill.invoice = @invoice", con);

cmd.Parameters.Add("@invoice", Convert.ToInt32(txtinvoice.Text) );  
cmd.ExecuteNonQuery();

---

单引号用于字符，如果您的

发票

为数字类型，则需要删除这些引号，如

tbbill.invoice = " + Convert.ToInt32(txtinvoice.Text) + ...

但不要用这种方式。 始终使用。这种类型的字符串连接对攻击是开放的

并使用自动处理命令和连接，而不是手动调用

dispose

方法

using(OleDbConnection con = new OleDbConnection(conString))
using(OleDbCommand cmd = con.CreateCommand())
{
    cmd.CommandText = "DELETE tbbill.*, tbgrid.* FROM tbbill INNER JOIN tbgrid ON tbbill.invoice = tbgrid.ginovice WHERE tbbill.invoice = @invoice";
    cmd.Parameters.Add("@invoice", OleDbType.Integer).Value = Convert.ToInt32(txtinvoice.Text);
    // I used OleDbType.Integer in my example. You should use proper OleDbType for your column.
    con.Open();
    cmd.ExecuteNonQuery();
}

---

您的

发票是字符还是数字？你应该经常使用。这种字符串串接容易受到攻击。它是数值型的
using(OleDbConnection con = new OleDbConnection(conString))
using(OleDbCommand cmd = con.CreateCommand())
{
    cmd.CommandText = "DELETE tbbill.*, tbgrid.* FROM tbbill INNER JOIN tbgrid ON tbbill.invoice = tbgrid.ginovice WHERE tbbill.invoice = @invoice";
    cmd.Parameters.Add("@invoice", OleDbType.Integer).Value = Convert.ToInt32(txtinvoice.Text);
    // I used OleDbType.Integer in my example. You should use proper OleDbType for your column.
    con.Open();
    cmd.ExecuteNonQuery();
}