Question

winform项目连接数据库用chart画柱状图

帮我看看这么链接数据库能不能读取到数据，我运行了感觉读不到数据，这个怎么改额，也不报错

Answer 1

给你个示例代码，自己对照下，你数据库链接没open,command也没有执行
private static void ConnectToData(string connectionString)
{ //Create a SqlConnection to the Northwind database.
using (SqlConnection connection = new SqlConnection(connectionString))
{ //Create a SqlDataAdapter for the Suppliers table.
SqlDataAdapter adapter = new SqlDataAdapter(); // A table mapping names the DataTable.
adapter.TableMappings.Add("Table", "Suppliers"); // Open the connection.
connection.Open();
Console.WriteLine("The SqlConnection is open."); // Create a SqlCommand to retrieve Suppliers data.
SqlCommand command = new SqlCommand( "SELECT SupplierID, CompanyName FROM dbo.Suppliers;",
connection);
command.CommandType = CommandType.Text; // Set the SqlDataAdapter's SelectCommand.
adapter.SelectCommand = command; // Fill the DataSet.
DataSet dataSet = new DataSet("Suppliers");
adapter.Fill(dataSet); // Create a second Adapter and Command to get
// the Products table, a child table of Suppliers.
SqlDataAdapter productsAdapter = new SqlDataAdapter();
productsAdapter.TableMappings.Add("Table", "Products");

SqlCommand productsCommand = new SqlCommand( "SELECT ProductID, SupplierID FROM dbo.Products;",
connection);
productsAdapter.SelectCommand = productsCommand; // Fill the DataSet.
productsAdapter.Fill(dataSet); // Close the connection.
connection.Close();
Console.WriteLine("The SqlConnection is closed."); // Create a DataRelation to link the two tables
// based on the SupplierID.
DataColumn parentColumn =
dataSet.Tables["Suppliers"].Columns["SupplierID"];
DataColumn childColumn =
dataSet.Tables["Products"].Columns["SupplierID"];
DataRelation relation = new System.Data.DataRelation("SuppliersProducts",
parentColumn, childColumn);
dataSet.Relations.Add(relation);
Console.WriteLine( "The {0} DataRelation has been created.",
relation.RelationName);
}
}