c#/ oop noob here。我正在从SQL Server数据库的模式创建一个数据表。我想要一个按钮,让用户从这个模式中选择一些表并执行某些操作(例如插入行)。但是,该方法无法引用我的第一个方法的数据表 - 如何从另一个方法引用第一个方法中的数据表?
以下是我正在使用的代码:
public Form1()
{
/****************************************************************/
string sqlSchema = " SELECT TABLE_CATALOG AS tblname ";
sqlSchema += " , TABLE_SCHEMA AS tblschema ";
sqlSchema += " , TABLE_NAME AS tblname ";
sqlSchema += " , COLUMN_NAME AS colname ";
sqlSchema += " , DATA_TYPE AS DATA_TYPE ";
sqlSchema += " , CHARACTER_MAXIMUM_LENGTH AS colsize ";
sqlSchema += " FROM INFORMATION_SCHEMA.COLUMNS ";
InitializeComponent();
OleDbConnection cn = new OleDbConnection(@"Provider=SQLNCLI;Server=THINK\SQLExpress;Database=Northwind;Trusted_Connection=yes;");
OleDbDataAdapter da = new OleDbDataAdapter(sqlSchema, cn);
DataTable dt = new DataTable();
da.TableMappings.Add("Table","Schema");
da.Fill(dt);
dataGridView1.DataSource = dt;
}
public void sql_PopulateTable(string tablenm, int rows)
{
// error on this line:
DataTable table1 = da.Tables["Schema"];
}
我得到的错误是“da”在当前上下文中无法识别。我应该将我的sqlSchema变量声明为静态吗?我该怎么做呢?
谢谢 -
答案 0 :(得分:0)
您的变量是在Form1构造函数的范围内声明的 - 因此一旦构造函数退出,变量就会被销毁。
您需要创建一个类级属性或变量来包含您的信息,以便所有方法都可以访问它。
public Form1()
{
/****************************************************************/
string sqlSchema = " SELECT TABLE_CATALOG AS tblname ";
sqlSchema += " , TABLE_SCHEMA AS tblschema ";
sqlSchema += " , TABLE_NAME AS tblname ";
sqlSchema += " , COLUMN_NAME AS colname ";
sqlSchema += " , DATA_TYPE AS DATA_TYPE ";
sqlSchema += " , CHARACTER_MAXIMUM_LENGTH AS colsize ";
sqlSchema += " FROM INFORMATION_SCHEMA.COLUMNS ";
InitializeComponent();
OleDbConnection cn = new OleDbConnection(@"Provider=SQLNCLI;Server=THINK\SQLExpress;Database=Northwind;Trusted_Connection=yes;");
Form1DataAdapter = new OleDbDataAdapter(sqlSchema, cn);
DataTable dt = new DataTable();
da.TableMappings.Add("Table","Schema");
da.Fill(dt);
dataGridView1.DataSource = dt;
}
public void sql_PopulateTable(string tablenm, int rows)
{
// error on this line:
DataTable table1 = Form1DataAdapter.Tables["Schema"];
}
public OleDbDataAdapter Form1DataAdapter { get; set; }
答案 1 :(得分:0)
为什么不使用GetSchema?
SqlConnection connection =
new SqlConnection(connectionString);
connection.Open();
DataTable dt = connection.GetSchema();
connection.Close();