我收到错误,在本地窗口中我看到conSettings和connectionString值为null.我说ConfigurationManager为null是正确的,我需要创建一个新对象.也许我正在使用Access,也许我在App.config文件中遗漏了一些东西.请有人帮我解决这个问题.提前致谢.
App.config文件......
<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<appSettings>
<add key="MyDBConnectionString" value="Provider=Microsoft.Jet.OLEDB.4.0;Data
Source=E:\...\Database1.mdb"/>
</appSettings>
</configuration>
Form.cs文件......
private void btnShow_Click(object sender, EventArgs e)
{
ConnectionStringSettings conSettings = ConfigurationManager.ConnectionStrings["MyDBConnectionString"];
string connectionString = ConfigurationManager.ConnectionStrings["MyDBConnectionString"].ConnectionString; // error points here
try
{
con = new OleDbConnection(connectionString);
con.Open();
cmd = new OleDbCommand("SELECT * FROM Table1", con);
objReader = cmd.ExecuteReader();
while (objReader.Read())
{
txtID.Text = ds.Tables[0].Rows[rno][0].ToString();
CBAgeGroup.Text = ds.Tables[0].Rows[rno][1].ToString();
CBGender.Text = ds.Tables[0].Rows[rno][2].ToString();
CBCrimOffen.Text = ds.Tables[0].Rows[rno][3].ToString();
if (ds.Tables[0].Rows[rno][4] != System.DBNull.Value)
{
photo_aray = (byte[])ds.Tables[0].Rows[rno][4];
MemoryStream ms = new MemoryStream(photo_aray); …访问2003 vs 2010 c#
我看不出哪里出错了.没有错误,但没有更新数据.我有插入,删除和编辑工作,但我不知道为什么我不能让它工作.请有人在此帮助我,提前谢谢......
连接字符串
myCon = new OleDbConnection(@"Provider=Microsoft.Jet.OLEDB.4.0;Data
Source=C:..\TempDB.mdb");
更新方法......
private void btnUpdate_Click(object sender, EventArgs e)
{
OleDbCommand cmd = new OleDbCommand();
cmd.CommandType = CommandType.Text;
cmd.CommandText = "UPDATE [Family] SET [FirstName] = ?, [LastName] = ?, [FamilyDOB] = ?, [Medical] = ? WHERE [ID] = ?";
//tried this as well
//cmd.CommandText = "UPDATE [Family] SET [FirstName] = FirstName, [LastName] = @LastName, [DOB] = @StudentDOB, [Medical] = @Medical WHERE [ID] = @ID";
cmd.Parameters.AddWithValue("@ID", txtFamID.Text);
cmd.Parameters.AddWithValue("@FirstName", txtFirstName.Text);
cmd.Parameters.AddWithValue("@LastName", txtLastName.Text);
cmd.Parameters.AddWithValue("@FamDOB", …我正在看一个网络教程,讲师用我不懂的语言讲话,视频没有显示完整的长度.任何人都可以告诉我这条线应该是什么样的......
private void Insertbtn_Click(object sender, EventArgs e)
{
OleDbCommand cmd = new OleDbCommand(); // this is good
cmd.CommandType = CommandType.Text; // this is good
cmd.CommandType = "INSERT INTO Students(StudentID, StudentName, StudentCNCI,
StudentDOB) Values('" + StudIDTxt.Text + "','" + StudNameTxt.Text + "','" +
StudCNCITxt.Text + "','" + StudDOBTxt.Text +")"; *// Need help here pls*
cmd.Connection=myCon;
myCon.Open();
cmd.ExecuteNonQuery();
myCon.Close();
}
我正在开发VS 2010 C#.使用Access.
我知道为什么我收到错误,我不知道代码是什么
我得到的错误是
must declare the scalar variable "@OTitle@FirstName"
我的方法看起来像这样..
cmd.CommandText = "INSERT into MainTable(ID, Title, OTitle, FirstName, LastName,...
VALUES(@ID, @Title, @OTitle" +
"@FirstName, @LastName, @MiddleName..)";
我知道+符号不起作用,所以我的问题是如何继续下一行.
如果有人可以帮助我,请提前致谢
在表单1中我放置了Comboxbox组件,我已经完成了这个...
string value = cBAdmin.Text;
我希望将Comboxbox保留在表单1中,但我希望从另一个类调用Comboxbox并完成剩余的编码.我该怎么做呢？如果有人可以帮助我,请提前感谢.
我收到错误,必须声明标量变量"@ID".指向ExecuteScalar行.我看着护目镜,我认为它与ID的插入参数有关.然后我再次读到可能存在拼写错误.在我的数据库中,我将列名称声明为ID,将数据类型声明为int,将"Is Identity"设置为是.由于我不打算手动插入ID列,我认为这就是我遇到问题的原因,我不知道如何解决这个问题.
我想要做的是插入用户名,登录日期和时间.用户注销时更新同一列(相同的id列).当用户再次登录时创建一个新列,依此类推.当我和D Stanley帮助我的时候,我正在使用我在这里和这里问过的类似代码.
如果有人可以帮助我,请提前致谢.
private int ID // forgot to add this.
{ get; set; }
private void btnLogin_Click(object sender, RoutedEventArgs e)
{
string value = cbRoles.Text;
switch (value)
{
case "Manager":
myCon.connectionString();
string dString = string.Empty;
SqlConnection thisConnection = myCon.dbCon;
SqlCommand nonqueryCommand = thisConnection.CreateCommand();
using (var command = myCon.dbCon.CreateCommand())
{
command.CommandText = "SELECT * FROM tblPrivileges";
command.Parameters.AddWithValue("UserName", (txtUserName.Text));
command.Parameters.AddWithValue("Password", (txtPassword.Text));
thisConnection.Open();
var reader = command.ExecuteReader(); //strcomp
{
if (reader.HasRows)
{
while (reader.Read()) …