C# 查询中缺少数据绑定oledb异常运算符

代码：

现在，我的datagridview正好显示了我想要的内容，因此它只是表示查询“sql”工作正常。只有当我通过单击“保存”按钮编辑并尝试绑定时，问题才会出现。我得到的错误是：

//this is in private void Form3_Load(object sender, EventArgs e)
{string sql = "select * from doctofact WHERE (([doctofact].[docid]=" + l + " and     [doctofact].[1userid]='"+str6+"'))";
  da = new OleDbDataAdapter(sql, con);
        cmd = new OleDbCommandBuilder(da);
        dt = new DataTable();
        BindingSource dsource = new BindingSource();
        dsource.DataSource = dt;
        da.Fill(dt);
        dataGridView1.DataSource = dt;
          dataGridView1.ReadOnly = true;


        da.Update(dt);
      }


  private void button3_Click(object sender, EventArgs e) // edit button
    {
        dataGridView1.ReadOnly = false;

        MessageBox.Show("Click on the cell you want to edit and change");
     }


      private void button4_Click(object sender, EventArgs e) //save button
    {
        da.Update(dt);
        MessageBox.Show("The changes you made have been saved!");
    }

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我会建议你通过这个链接。

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问题是由于数据类型不匹配造成的

我使用了相同的教程编写查询。如果数据类型有问题，我相信即使我的插入查询也不会工作。但它工作得很好，我可以在datagridview中看到我需要什么。这个错误似乎暗示了一些简单的事情。

 oledb exception missing operator in the query Syntax error (missing operator) in query expression '(((? = 1 AND DocID IS NULL) OR (DocID = ?)) AND ((? = 1 AND FactID IS NULL) OR (FactID = ?)) AND ((? = 1 AND ArticleTitle IS NULL) OR (ArticleTitle = ?)) AND ((? = 1 AND FactPreview IS NULL) OR (FactPreview = ?)) AND ((? = 1 AND 1userid IS NULL) OR (1user'.