我有一个Windows窗体（在VisualStudio-10中），可以将条目加载/保存到数据库，导航现有条目并在表单中编辑它们。我想要做的是每次创建新条目时，表单编号（每个条目的4位主键）从Access DB表中的最后一个条目递增1。
有没有办法调用最后一个条目的索引，将其递增1并将该数字打印到表单编号文本框？到目前为止，我在搜索中找不到大量有用的信息，所以如果你能指出我正确的方向或另一个问题，我们将不胜感激，谢谢。
这是db的更新功能/连接。数据库名称为 servicereq1 ，表名为 servicereq 。我希望显示更新密钥的文本框是 serviceRequestNumberTextBox 。再次感谢您的帮助。
private void updateButton_Click_1(object sender, EventArgs e)
{
{
OleDbConnection conn = new OleDbConnection();
AppDomain.CurrentDomain.SetData("DataDirectory", @"\\prod\ServiceRequests");
conn.ConnectionString = @"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=|DataDirectory|\servicereq1.mdb";
OleDbCommand cmd = new OleDbCommand("UPDATE servicereq SET ServiceRequestNumber = @servreq, DateLogged = @datelogged, LoggedBy = @loggedby, [Problem In Environment] = @problemfoundin, Function = @function, [Other Impacts] = @summary, Account = @earningsaccount, [From] = @from, [To] = @to, Status = @status, Description = @description, Fixer = @fixer, [Time Estimate] = @timeestimate, [Actual Start] = @actualstart, [Actual Finish] = @actualfinish, [Actual Time] = @actualtime, [Programs/Forms] = @programsforms, Comments = @comments, [Retest Date] = @requestdate, Tester = @tester, [Code In Environment] = @codein WHERE (ServiceRequestNumber = @servreq)");
cmd.Connection = conn;
conn.Open();
if (conn.State == ConnectionState.Open)
{
cmd.Parameters.AddWithValue("@servreq", serviceRequestNumberTextBox.Text);
cmd.Parameters.AddWithValue("@datelogged", dateLoggedTextBox.Text);
cmd.Parameters.AddWithValue("@loggedby", loggedByComboBox.Text);
cmd.Parameters.AddWithValue("@problemfoundin", problem_In_EnvironmentComboBox.Text);
cmd.Parameters.AddWithValue("@function", functionTextBox.Text);
cmd.Parameters.AddWithValue("@summary", other_ImpactsTextBox.Text);
cmd.Parameters.AddWithValue("@earningsaccount", accountTextBox.Text);
cmd.Parameters.AddWithValue("@from", fromTextBox.Text);
cmd.Parameters.AddWithValue("@to", toTextBox.Text);
cmd.Parameters.AddWithValue("@status", statusComboBox.Text);
cmd.Parameters.AddWithValue("@description", descriptionTextBox.Text);
cmd.Parameters.AddWithValue("@fixer", fixerComboBox.Text);
cmd.Parameters.AddWithValue("@timeestimate", time_EstimateTextBox.Text);
cmd.Parameters.AddWithValue("@actualstart", actual_StartTextBox.Text);
cmd.Parameters.AddWithValue("@actualfinish", actual_FinishTextBox.Text);
cmd.Parameters.AddWithValue("@actualtime", actual_TimeTextBox.Text);
cmd.Parameters.AddWithValue("@programsforms", programs_FormsTextBox.Text);
cmd.Parameters.AddWithValue("@comments", commentsTextBox.Text);
cmd.Parameters.AddWithValue("@requestdate", retest_DateTextBox.Text);
cmd.Parameters.AddWithValue("@tester", testerComboBox.Text);
cmd.Parameters.AddWithValue("@codein", code_In_EnvironmentComboBox.Text);
cmd.Parameters.AddWithValue("@servreq", serviceRequestNumberTextBox.Text);
try
{
cmd.ExecuteNonQuery();
MessageBox.Show("Form Updated Successfully");
conn.Close();
}
catch (OleDbException ex)
{
MessageBox.Show(ex.Message);
conn.Close();
}
}
else
{
MessageBox.Show("Connection Failed");
}
}
}
这是保存新记录功能。
private void updateButton_Click(object sender, EventArgs e)
{
{
OleDbConnection conn = new OleDbConnection();
AppDomain.CurrentDomain.SetData("DataDirectory", @"\\prod\ServiceRequests");
conn.ConnectionString = @"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=|DataDirectory|\servicereq1.mdb";
String servreq = serviceRequestNumberTextBox.Text;
String datelogged = dateLoggedTextBox.Text;
String loggedby = loggedByComboBox.Text;
String problemfoundin = problem_In_EnvironmentComboBox.Text;
String function = functionTextBox.Text;
String summary = other_ImpactsTextBox.Text;
String earningsaccount = accountTextBox.Text;
String from = fromTextBox.Text;
String to = toTextBox.Text;
String status = statusComboBox.Text;
String description = descriptionTextBox.Text;
String fixer = fixerComboBox.Text;
String codein = code_In_EnvironmentComboBox.Text;
String programsforms = programs_FormsTextBox.Text;
String timeestimate = time_EstimateTextBox.Text;
String actualstart = actual_StartTextBox.Text;
String actualfinish = actual_FinishTextBox.Text;
String actualtime = actual_TimeTextBox.Text;
String retestdate = retest_DateTextBox.Text;
String tester = testerComboBox.Text;
String comments = commentsTextBox.Text;
OleDbCommand cmd = new OleDbCommand("INSERT into servicereq ([ServiceRequestNumber], DateLogged, LoggedBy, [Problem In Environment], Function, [Other Impacts], Account, [From], [To], Status, Description, Fixer, [Code In Environment], [Programs/Forms], [Time Estimate], [Actual Start], [Actual Finish], [Actual Time], [Retest Date], Tester, Comments) Values(@servreq, @datelogged, @loggedby, @problemfoundin, @function, @summary, @earningsaccount, @from, @to, @status, @description, @fixer, @codein, @programsforms, @timeestimate, @actualstart, @actualfinish, @actualtime, @requestdate, @tester, @comments)");
cmd.Connection = conn;
conn.Open();
if (conn.State == ConnectionState.Open)
{
cmd.Parameters.Add("@servreq", OleDbType.VarChar).Value = servreq;
cmd.Parameters.Add("@datelogged", OleDbType.VarChar).Value = datelogged;
cmd.Parameters.Add("@loggedby", OleDbType.VarChar).Value = loggedby;
cmd.Parameters.Add("@problemfoundin", OleDbType.VarChar).Value = problemfoundin;
cmd.Parameters.Add("@function", OleDbType.VarChar).Value = function;
cmd.Parameters.Add("@summary", OleDbType.VarChar).Value = summary;
cmd.Parameters.Add("@earningsaccount", OleDbType.VarChar).Value = earningsaccount;
cmd.Parameters.Add("@from", OleDbType.VarChar).Value = from;
cmd.Parameters.Add("@to", OleDbType.VarChar).Value = to;
cmd.Parameters.Add("@status", OleDbType.VarChar).Value = status;
cmd.Parameters.Add("@description", OleDbType.VarChar).Value = description;
cmd.Parameters.Add("@fixer", OleDbType.VarChar).Value = fixer;
cmd.Parameters.Add("@codein", OleDbType.VarChar).Value = codein;
cmd.Parameters.Add("@programsforms", OleDbType.VarChar).Value = programsforms;
cmd.Parameters.Add("@timeestimate", OleDbType.VarChar).Value = timeestimate;
cmd.Parameters.Add("@actualstart", OleDbType.VarChar).Value = actualstart;
cmd.Parameters.Add("@actualfinish", OleDbType.VarChar).Value = actualfinish;
cmd.Parameters.Add("@actualtime", OleDbType.VarChar).Value = actualtime;
cmd.Parameters.Add("@requestdate", OleDbType.VarChar).Value = retestdate;
cmd.Parameters.Add("@tester", OleDbType.VarChar).Value = tester;
cmd.Parameters.Add("@comments", OleDbType.VarChar).Value = comments;
try
{
cmd.ExecuteNonQuery();
MessageBox.Show("Form Submitted Successfully");
servicereqBindingSource.ResetBindings(true);
conn.Close();
}
catch (OleDbException ex)
{
MessageBox.Show(ex.Message);
conn.Close();
}
}
else
{
MessageBox.Show("Connection Failed");
}
this.servicereqTableAdapter1.Load(servicereq1DataSet2.servicereq, serviceRequestNumberTextBox.Text);
}
}
答案 0 :(得分：4)
像这样的多用户场景中的正确方法是将ServiceRequestNumber字段更改为AUTONUMBER字段。通过这种方式，数据库引擎可以计算新的数字，并且您不会冒险将同一个号码分配给在同一数据库中工作但来自两台不同PC的不同用户的情况。
当然，您不需要在此字段的INSERT查询中传递任何内容，因此请从INSERT查询文本中删除ServerRequestNumber及其参数占位符。
如果你想知道分配给你的记录的AUTONUMBER是什么，你可以写这个sql
using(OleDbConnection conn = new OleDbConnection(......))
using(OleDbCommand cmd = new OleDbCommand("SELECT @@IDENTITY", conn))
{
conn.Open();
int newServiceRequestNumber = Convert.ToInt32(cmd.ExecuteScalar());
....
}
请注意，您应该将连接和其他一次性物品放在使用区域内，以确保它们处理和关闭
答案 1 :(得分：2)
正如史蒂夫在评论中所说，最简单的方法是将colunm设置为数据库中的自动编号，只需在添加新条目的表单中删除id的文本框即可。在INSERT命令中，不要为id赋予任何值，数据库将自动为该新条目生成一个新数字（最后一个id + 1）。