将ArrayList对象转换为double [英] convert ArrayList object to double
问题描述
在下面的代码中，我希望ArrayList对象x的类型为double。
我该怎么做？
- -Thanks
SqlConnection objConnection = new
SqlConnection（" server =（local）\\SQLEXPRESS; database = Northwind; integrated
security = true;"）;
String strSQL =" SELECT ProductName，UnitsInStock FROM Products
WHERE UnitsInStock> = 50" ;;
SqlCommand objCommand = new SqlCommand（strSQL，objConnection）;
objConnection.Open（）;
ArrayList strLabel = new ArrayList（）;
ArrayList x = new ArrayList（）;
SqlDataReader dr = objCommand.ExecuteReader（）;
while（dr.Read（））
{
object [] values1 = new object [0];
dr.GetValues （values1）;
strLabel.Add（values1）;
object [] values2 = new object [1];
dr.GetValues（values2）;
x.Add（values2） ;
}
dr.Close（）;
objConnection.Close（）;
你需要CLR 2.0泛型...
List< double> x =新列表< double>（）;
Web学习者写道：在下面的代码中，我希望ArrayList对象x的类型为double。
我该怎么办？
- 谢谢
SqlConnection objConnection = new
SqlConnection（" server =（local） \\SQLEXPRESS; database = Northwind; integrated
security = true;"）;
String strSQL =" SELECT ProductName，UnitsInStock FROM Products
WHERE UnitsInStock> = 50" ;;
SqlCommand objCommand = new SqlCommand（strSQL，objConnection）;
objConnection.Open（）;
ArrayList strLabel = new ArrayList（）;
ArrayList x = new ArrayList（）;
SqlDataReader dr = objCommand.ExecuteReader（）;
while（dr.Read（））
{
对象[] values1 =新对象[0];
dr.GetValues（values1 ）;
strLabel.Add（values1）;
object [] values2 = new object [1];
dr.GetValues（values2）;
x.Add （values2）;
}
dr.Close（）;
objConnection.Close（）;
我更改了代码如下。
List< string> ProductName = new List< string>（）;
List< double> UnitsInStock =新列表< double>（）;
SqlDataReader dr = objCommand.ExecuteReader（）;
while（dr.Read（））
{
ProductName.Add（dr.GetValue（0））;
UnitsInStock.Add（dr.GetValue（1））;
}
现在我收到以下错误。
''System.Collections.Generic的最佳重载方法匹配。 List< string> .Add（strin g）''有一些无效的参数
最好的重载方法匹配''System.Collections.Generic.List< double> .Add（doubl） e）''有一些无效的论点
还有什么想法吗？
-
< ag ****** @ gmail.com>在留言新闻中写道：11 ********************** @ g10g2000cwb.googlegr oups.com ...你需要CLR 2.0那个泛型......
List< double> x =新列表< double>（）;
Web学习者写道：在下面的代码中，我希望ArrayList对象x的类型为double。
我该怎么做？
- 谢谢
SqlConnection objConnection = new
SqlConnection（" server =（local）\\ SQLEXPRESS; database = Northwind; integrated
security = true;"）;
String strSQL =" SELECT ProductName，UnitsInStock FROM Products
WHERE UnitsInStock> = 50";
SqlCommand objCommand = new SqlCommand（strSQL，objConnection）;
objConnection.Open（）;
ArrayList strLabel = new ArrayList（）;
ArrayList x = new ArrayList （）;
SqlDataReader dr = objCommand.ExecuteReader（）;
while（dr.Read（））
{
object [] values1 =新对象[0];
dr.GetValues（values1）;
strLabel.Add（values1）;
object [] values2 = new object [1];
dr.GetValues（values2）;
x.Add（values2）;
}
dr.Close（）;
objConnection.Close（）;
< blockquote>如果您知道数据行中的第一项是字符串，
，第二项是双精度，并且它们都不能为空，那么
你可以这样做：
ProductName.Add（（string）dr.GetValue（0））;
UnitsInStock.Add（（double） Dr.GetValue（1））;
In the following code, I want ArrayList object x to be of type double.
How can I do that?
--Thanks
SqlConnection objConnection = new
SqlConnection("server=(local)\\SQLEXPRESS; database=Northwind; integrated
security=true;");
String strSQL = "SELECT ProductName, UnitsInStock FROM Products
WHERE UnitsInStock >= 50";
SqlCommand objCommand = new SqlCommand(strSQL, objConnection);
objConnection.Open();
ArrayList strLabel = new ArrayList();
ArrayList x = new ArrayList();
SqlDataReader dr = objCommand.ExecuteReader();
while (dr.Read())
{
object[] values1 = new object[0];
dr.GetValues(values1);
strLabel.Add(values1);
object[] values2 = new object[1];
dr.GetValues(values2);
x.Add(values2);
}
dr.Close();
objConnection.Close();
You need CLR 2.0 generics for that...
List<double> x = new List<double>( );
Web learner wrote:In the following code, I want ArrayList object x to be of type double.
How can I do that?
--Thanks
SqlConnection objConnection = new
SqlConnection("server=(local)\\SQLEXPRESS; database=Northwind; integrated
security=true;");
String strSQL = "SELECT ProductName, UnitsInStock FROM Products
WHERE UnitsInStock >= 50";
SqlCommand objCommand = new SqlCommand(strSQL, objConnection);
objConnection.Open();
ArrayList strLabel = new ArrayList();
ArrayList x = new ArrayList();
SqlDataReader dr = objCommand.ExecuteReader();
while (dr.Read())
{
object[] values1 = new object[0];
dr.GetValues(values1);
strLabel.Add(values1);
object[] values2 = new object[1];
dr.GetValues(values2);
x.Add(values2);
}
dr.Close();
objConnection.Close();
I changed the code as follows.
List<string> ProductName = new List<string>();
List<double> UnitsInStock = new List<double>();
SqlDataReader dr = objCommand.ExecuteReader();
while (dr.Read())
{
ProductName.Add(dr.GetValue(0));
UnitsInStock.Add(dr.GetValue(1));
}
Now I get the following errors.
The best overloaded method match for ''System.Collections.Generic.List<string>.Add(strin g)'' has some invalid arguments
The best overloaded method match for ''System.Collections.Generic.List<double>.Add(doubl e)'' has some invalid arguments
Any further idea, please??
--
<ag******@gmail.com> wrote in message news:11**********************@g10g2000cwb.googlegr oups.com...You need CLR 2.0 generics for that...
List<double> x = new List<double>( );
Web learner wrote:In the following code, I want ArrayList object x to be of type double.
How can I do that?
--Thanks
SqlConnection objConnection = new
SqlConnection("server=(local)\\SQLEXPRESS; database=Northwind; integrated
security=true;");
String strSQL = "SELECT ProductName, UnitsInStock FROM Products
WHERE UnitsInStock >= 50";
SqlCommand objCommand = new SqlCommand(strSQL, objConnection);
objConnection.Open();
ArrayList strLabel = new ArrayList();
ArrayList x = new ArrayList();
SqlDataReader dr = objCommand.ExecuteReader();
while (dr.Read())
{
object[] values1 = new object[0];
dr.GetValues(values1);
strLabel.Add(values1);
object[] values2 = new object[1];
dr.GetValues(values2);
x.Add(values2);
}
dr.Close();
objConnection.Close();
If you know for a fact that the first item in the data row is a string,
and the second is a double, and neither of them can ever be null, then
you can do this:
ProductName.Add((string)dr.GetValue(0));
UnitsInStock.Add((double)dr.GetValue(1));
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