c# - 插入前检查重复项 (C#.net)

Question

我有一个文本框表格，学生可以填写他们的一般信息，例如名字和姓氏、城市、州等。有时学生不记得他们以前是否填写过表格，这会导致重复输入在 ms-access 数据库中。理想情况下，我希望代码在插入之前首先在 ms-access 数据库中搜索同一记录上匹配的名字和姓氏。如果有一条记录与输入的名字和姓氏字段都匹配，那么将运行一个脚本并说出类似“匹配的记录已经存在，你想继续吗？”之类的话。单击"is"会将记录输入新行，单击“取消”则根本不会将其输入数据库。

我开始了这段代码，但我不确定它是否是正确的方向，任何指导将不胜感激，谢谢。

using (OleDbConnection con = new OleDbConnection(constr))
    using (OleDbCommand com = new OleDbCommand("SELECT COUNT(*) FROM StudentList WHERE [FName] = @FName AND [LName] = @LName", con))
    {
        con.Open();
        using (OleDbDataReader myReader = com.ExecuteReader())
        {
            (This is where I am stuck)
        }
    }

下面是提交按钮的当前代码。

protected void btnSubmit_Click(object sender, EventArgs e)
{
    {
        //Preforms insert statement on click to allow additions to the database
        DateTime CurrentDate;
        CurrentDate = DateTime.Now;

        string constr = @"Provider=Microsoft.Jet.OLEDB.4.0; Data Source=D:\sites\schoolinfo\students_dev\App_Data\Studentdb.mdb";
        string cmdstr = "INSERT into StudentList(FName, LName, BDay, Gender, School, Grade, Address, APT, City, State, Zip, Email, Phone, CellPhone, ParentFName, ParentLName, ParentEmail) values(@FName, @LName, @BDay, @Gender, @School, @Grade, @Address, @APT, @City, @State, @Zip, @Email, @Phone, @CellPhone, @ParentFName, @ParentLName, @ParentEmail)";



        OleDbConnection con = new OleDbConnection(constr);
        OleDbCommand com = new OleDbCommand(cmdstr, con);
        {
            con.Open();
        }
        //The following fields are added from the student information to the corresponding database fields
        com.Parameters.AddWithValue("@FName", txtFirstName.Text);
        com.Parameters.AddWithValue("@LName", txtLastName.Text);
        com.Parameters.AddWithValue("@BDay", txtBirthDate.Text);
        com.Parameters.AddWithValue("@Gender", ddlGender.Text);
        com.Parameters.AddWithValue("@School", txtSchool.Text);
        com.Parameters.AddWithValue("@Grade", txtGrade.Text);

        //The following fields are added from the contact information to the corresponding database fields
        com.Parameters.AddWithValue("@Address", txtAddress.Text);
        com.Parameters.AddWithValue("@APT", txtApt.Text);
        com.Parameters.AddWithValue("@City", txtCity.Text);
        com.Parameters.AddWithValue("@State", ddlState.Text);
        com.Parameters.AddWithValue("@Zip", txtZip.Text);
        com.Parameters.AddWithValue("@Email", txtEmail.Text);
        com.Parameters.AddWithValue("@Phone", txtPhone.Text);
        com.Parameters.AddWithValue("@CellPhone", txtCellPhone.Text);
        com.Parameters.AddWithValue("@ParentFName", txtParentFName.Text);
        com.Parameters.AddWithValue("@ParentLName", txtParentLName.Text);
        com.Parameters.AddWithValue("@ParentEmail", txtParentEmail.Text);
        com.ExecuteNonQuery();
        con.Close();

        //End database connection
        ScriptManager.RegisterClientScriptBlock(this, this.GetType(), "alertMessage", "alert('Student has been successfully added!')", true);
    }
}

Answer 1

using (OleDbConnection con = new OleDbConnection(constr))
    using (OleDbCommand com = new OleDbCommand("SELECT COUNT(*) FROM StudentList WHERE [FName] = @FName AND [LName] = @LName", con))
    {
        // Add your @Fname and @LName parameters here
        com.Parameters.AddWithValue("@FName", firstName);
        com.Parameters.AddWithValue("@LName", lastName);

        con.Open();
        using (OleDbDataReader myReader = com.ExecuteReader())
        {
            myReader.Read();
            int count = myReader.GetInt32(0);
            // return count > 0 or whatever to indicate that it exists
        }
    }