C# 不能使用c返回多个SQL行数据
我有一个数据库,我在其中存储多行及其点、颜色、宽度等。我知道这些点正在被存储,因为我检查了SQL表,它就在那里。但是,当我尝试重新加载这些点时,它只会加载我存储的最后一行。我不明白这是为什么C# 不能使用c返回多个SQL行数据,c#,sql,sql-server,C#,Sql,Sql Server,我有一个数据库,我在其中存储多行及其点、颜色、宽度等。我知道这些点正在被存储,因为我检查了SQL表,它就在那里。但是,当我尝试重新加载这些点时,它只会加载我存储的最后一行。我不明白这是为什么 private void opendbtestToolStripMenuItem_Click(object sender, EventArgs e) { try { using (SqlConnection conn = new SqlCo
private void opendbtestToolStripMenuItem_Click(object sender, EventArgs e)
{
try
{
using (SqlConnection conn = new SqlConnection("blahblabhblah; "))
{
conn.Open();
using (SqlCommand cmd = new SqlCommand("SELECT * FROM Line", conn))
{
using (SqlDataReader reader = cmd.ExecuteReader())
{
while (reader.Read())
{
Shape Line = new Line(); // New line
Line.readSQL();
shapeList.Add(Line);
Invalidate();
}
}
}
conn.Close();
}
}
catch(Exception ex)
{
MessageBox.Show(ex.Message);
}
}
readSQL函数
public override void readSQL()
{
try
{
using (SqlConnection conn = new SqlConnection("blahblahblah; "))
{
conn.Open();
using (SqlCommand cmd = new SqlCommand("SELECT * FROM Line", conn))
{
using (SqlDataReader reader = cmd.ExecuteReader())
{
if (reader != null)
{
while (reader.Read())
{
// string s = (reader["ID"].ToString());
int x1 = Convert.ToInt32(reader["x1"]);
int x2 = Convert.ToInt32(reader["x2"]);
int y1 = Convert.ToInt32(reader["y1"]);
int y2 = Convert.ToInt32(reader["y2"]);
Pt1 = new Point(x1, y1);
Pt2 = new Point(x2, y2);
PenWidth = Convert.ToInt32(reader["Width"]);
PenColor = Color.FromArgb(Convert.ToInt32(reader["Color"]));
}
}
}
}
conn.Close();
}
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
// MessageBox.Show(PenColor.ToString());
// MessageBox.Show(PenWidth.ToString());
}
}
如何写入数据库
public override void writeSQL()
{
using (SqlConnection conn = new SqlConnection("blahblahblah "))
{
using (SqlCommand comm = new SqlCommand())
{
comm.Connection = conn;
comm.CommandType = CommandType.Text;
comm.CommandText = "INSERT INTO Line (x1,x2,y1,y2, Width, Color) VALUES (@val1, @val2, @val3, @val4, @val5, @val6)";
comm.Parameters.AddWithValue("@val1", Pt1.X);
comm.Parameters.AddWithValue("@val2", Pt2.X);
comm.Parameters.AddWithValue("@val3", Pt1.Y);
comm.Parameters.AddWithValue("@val4", Pt2.Y);
comm.Parameters.AddWithValue("@val5", PenWidth);
comm.Parameters.AddWithValue("@val6", PenColor.ToArgb());
try
{
conn.Open();
comm.ExecuteNonQuery();
MessageBox.Show("Insertion complete");
}
catch (Exception ex)
{
MessageBox.Show(ex.Message, "fuuuu");
}
}
conn.Close();
}
}
我想你应该试试这个。执行查询并将所有数据加载到datatable中。之后,您可以循环浏览每条记录
string query = "SELECT * FROM Line";
using (SqlCommand cmd = new SqlCommand(query, conn))
{
DataTable dt = new DataTable();
dt.Load(cmd.ExecuteReader());
foreach (DataRow row in dt.Rows)
{
//manipulate your data
}
}
将sqlDataReader发送到另一个函数并操作该函数中的数据,如下所示:
public bool InitializeVariables(SqlDataReader sdr, bool isSingle = true)
{
try
{
if (sdr.HasRows)
{
if (isSingle)
sdr.Read();
//initialize and manipulate data here.
return true;
}
else
return false;
}
catch (System.Exception ex)
{
throw ex;
}
}
根据您的代码,线是一个单一的对象。您正在对一个Line对象调用ReadSQL作为一个非静态方法,并期望它返回多行,但这并没有真正意义——您的方法在当前对象上设置了两个属性,因此根据定义,只返回集合中的最后一项
如果ReadSQL中的代码是为特定Id选择的,则它更有意义,例如
using (var cmd = new SqlCommand("SELECT * FROM Line Where id = @id", conn))
{
cmd.Parameters.Add(new SqlParameter("Id", SqlDbType.Int) { Value = id });
//....
}
如果要返回行集合,则需要在Line对象上使用静态方法,或者在其他位置使用返回行对象集合的方法
public static IEnumerable<Line> GetLines(int id)
{
var returnData = new List<Line>();
try
{
using (var conn = new SqlConnection("blahblahblah; "))
using (var cmd = new SqlCommand("SELECT * FROM Line", conn))
{
conn.Open();
using (var reader = cmd.ExecuteReader())
{
while (reader.Read())
{
// string s = (reader["ID"].ToString());
int x1 = Convert.ToInt32(reader["x1"]);
int x2 = Convert.ToInt32(reader["x2"]);
int y1 = Convert.ToInt32(reader["y1"]);
int y2 = Convert.ToInt32(reader["y2"]);
returnData.Add(new Line()
{
Pt1 = new Point(x1, y1),
Pt2 = new Point(x2, y2),
PenWidth = Convert.ToInt32(reader["Width"]),
PenColor = Color.FromArgb(Convert.ToInt32(reader["Color"]))
});
}
}
conn.Close();
}
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
return returnData;
}
创建一个对象并将其添加到一个集合中,其中分配了Pt1、Pt2?为什么有两个SqlConnection/Command/Reader?我已经更新了原来的帖子,让它更清晰一些。有两个sqlconnections/command/reader,因为它们位于不同的文件中。@文斯,为什么在主线程中调用readsql函数,是否需要再次读取sql?亲爱的@文斯,Shape Line=new Line!!!!这是什么???形状线=新形状!!哪一个?