Question

C#调用类出现的问题错误 1 类、结构或接口成员声明中的标记“=”无效

form1里：
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.Data.SqlClient;

namespace WindowsApplication1
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}

private void btnShow_Click(object sender, EventArgs e)
{

string cmdText = "select * from manageMent";
SqlDataAdapter da = new SqlDataAdapter(cmdText,sqlCon);
DataTable dtManman = new DataTable();
try
{
sqlCon.Open();
da.Fill(dtManman);
}
catch (Exception ex)
{ MessageBox.Show(ex.Message); }
finally { sqlCon.Close(); }
dgvMan.DataSource = dtManman;
}

}
}

新建类Class1里：
using System;
using System.Collections.Generic;
using System.Text;

namespace WindowsApplication1
{
class Class1
{
string connectionstring = "Data Source=.;Database=pubs;Uid=sa;Pwd=sa";
SqlConnection sqlCon = new SqlConnection();
sqlCon.ConnectionString = connectionstring;
}
}
然后出现 ，求解决，调用类方面。

Answer 1

把sqlCon.ConnectionString = connectionstring;这句放到构造函数里

class Class1
{
    string connectionstring = "Data Source=.;Database=pubs;Uid=sa;Pwd=sa";
    SqlConnection sqlCon = new SqlConnection();
    public Class1()
    {
        sqlCon.ConnectionString = connectionstring;
    }
}

Answer 2

倒数第3行语法错误，要么构造初始化，要么使用时给连接串。

Answer 3

sqlCon.ConnectionString = connectionstring;这句赋值的语句，必须写在方法中，不能和定义一样直接写在类下面。
private void a()
{
sqlCon.ConnectionString = connectionstring;
}