小编Анд*_*Про的帖子

我有桌子 "学生"

   P_ID   LastName  FirstName  Address  City

   1        Hansen    Ola                
   2        Svendson   Tove
   3        Petterson   Kari
   4        Nilsen       Johan
...and so on 

如何在C#中更改编辑代码

 string firstName = "Ola";
 string  lastName ="Hansen";
 string  address = "ABC";
 string city = "Salzburg";

 string connectionString = System.Configuration.ConfigurationManager
                          .ConnectionStrings["LocalDB"].ConnectionString;

 using (SqlConnection connection = new SqlConnection(connectionString))
     using (SqlCommand command = connection.CreateCommand())
 { 
   command.CommandText = "INSERT INTO Student (LastName, FirstName, Address, City) 
                          VALUES (@ln, @fn, @add, @cit)";

   command.Parameters.AddWithValue("@ln", lastName);
   command.Parameters.AddWithValue("@fn", firstName);
   command.Parameters.AddWithValue("@add", address);
   command.Parameters.AddWithValue("@cit", city);

   connection.Open();

   command.ExecuteNonQuery();

   connection.Close(); …

我有程序,我有很多按钮.每个按钮的背景设置为

  <Button x:Name="mybutton"  HorizontalAlignment="Left" Height="30" Margin="76,110,0,0" VerticalAlignment="Top" Width="25" Click="some_click">
                <Button.Background>
                    <ImageBrush ImageSource="Resource/button_picture.png"/>
                </Button.Background>
</Button>

当程序没有运行时,图像显示为.xaml中的背景,但是当我运行应用程序图像时,图像不作为按钮的背景.如何在按钮中调试此背景？那里有任何愚蠢的错误吗？

可能重复:
变量名'@VarName'已被声明为Issue

using (SqlCommand command = connection.CreateCommand())
{
    int j = 1;
    for (int i = 0; i < temp4.Count; i++)
    {
        #region idsetter

        int prevId = 0;

        command.CommandText = "SELECT MAX(id) FROM Configuration";
        connection.Open();
        using (SqlDataReader reader = command.ExecuteReader())
        {
            while (reader.Read())
            {
                if (reader[0].ToString() != "")
                {
                    prevId = Int32.Parse(reader[0].ToString());
                }
                else
                {
                    prevId = 0;
                }
            }
        }

        connection.Close();
        int currId = prevId + 1;
        #endregion
        command.CommandText = "INSERT INTO Configuration (id,A, B, C, D, E, F,G) …

我有一份清单

Class =>       Second      Third   Second  Fourth  Fifth  Second

Position =>     2           3       2       5        1     3 

我想创建具有Same类和相同Positon的新列表

即新名单

Class  =>      Second       Second

Postion =>       2             2


Class  =>         Second

Position =>         3


Class  =>          Third

Position =>          3

等等

我可以在父列表上使用多个GroupBy来生成这些不同的列表,或者首先我应该GroupBy"Class"然后按"Position"？