c# - "Data type mismatch in criteria expression"尝试从数据库中删除行时

Question

    OleDbCommand system = new OleDbCommand();
    system.CommandType = CommandType.Text;
    system.CommandText = "DELETE FROM Student WHERE(ID= '" + 
                          txtStudentIDnumber.Text + "')";
    system.Connection = mydatabase;

    mydatabase.Open();
    system.ExecuteNonQuery();
    dataGridView1.Update();

    this.tableAdapterManager.UpdateAll(csharrpfinalprojectDataSet);
    mydatabase.Close();

    MessageBox.Show("Student Record Deleted.", "deleting record...");

Answer 1

在您的命令文本中，您需要删除 txtStudentIDnumber.Text 周围的单引号 (')，因为它显示 ID 是整数类型，并且您将其作为字符串传递.以下应该修复错误。

system.CommandText = "DELETE FROM Student WHERE(ID= " + txtStudentIDnumber.Text + ")";

编辑:关于@mdb 评论，您应该始终使用 Parameters在您的查询中，这样您就可以避免 SQL Injection .请考虑以下事项:

OleDbCommand system = new OleDbCommand();
system.CommandType = CommandType.Text;
system.CommandText = "DELETE FROM Student WHERE ID = ?";
OleDbParameter parameter = new OleDbParameter("ID", txtStudentIDnumber.Text);
system.Parameters.Add(parameter);
system.Connection = mydatabase;

mydatabase.Open();
system.ExecuteNonQuery();
dataGridView1.Update();