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c# - 错误：ConnectionString 属性尚未初始化

问题描述

            string extension = Path.GetExtension(@"Provider=Microsoft.Jet.OLEDB.4.0;Data Source='" + openFileDialog1.FileName + "'; Extended Properties=Excel 8.0;");

        using (System.Data.OleDb.OleDbConnection con = new System.Data.OleDb.OleDbConnection())
        {
            switch (extension)
            {
                case ".xls":
                    string xlsconStr = @"Provider=Microsoft.Jet.OLEDB.4.0;Data Source='" + openFileDialog1.FileName + "'; Extended Properties=Excel 8.0;";
                    con.ConnectionString = xlsconStr;
                    break;

                case ".xlsx":
                case ".xlsm":
                    string xlsxconStr = @"Provider=Microsoft.ACE.OLEDB.12.0;Data Source='" + openFileDialog1.FileName + "'; Extended Properties=Excel 12.0;";
                    con.ConnectionString = xlsxconStr;
                    break;
            }
                using (System.Data.OleDb.OleDbCommand oconn = new System.Data.OleDb.OleDbCommand("SELECT * FROM [" + listBox1.SelectedIndex.ToString() + "$]", con))
                {
                    // **There will be an error here**
                    // **The ConnectionString property has not been initialized.**
                    con.Open();

                    System.Data.OleDb.OleDbDataAdapter adapter = new System.Data.OleDb.OleDbDataAdapter(oconn);
                    System.Data.DataTable data = new System.Data.DataTable();
                    adapter.Fill(data);
                    dataGridView1.DataSource = data;
                }
        }

代码有什么问题？我的目的是在listBox上的selectedItem上绘制所有数据库，每当我单击它时，它都会填充dataGridView

顺便说一句，所选项目来自MSExcel 工作表名称

标签： c#excel

解决方案

您的代码需要很少的修复：

string extension = Path.GetExtension(openFileDialog1.FileName);

以前您的 GetExtension 试图在您的连接字符串上找到扩展名，该方法不可能，因为是连接字符串而不是路径！

所以你的代码固定应该是这样的：

    string extension = Path.GetExtension(openFileDialog1.FileName);

    using (System.Data.OleDb.OleDbConnection con = new System.Data.OleDb.OleDbConnection())
    {
        switch (extension)
        {
            case ".xls":
                string xlsconStr = @"Provider=Microsoft.Jet.OLEDB.4.0;Data Source='" + openFileDialog1.FileName + "'; Extended Properties=Excel 8.0;";
                con.ConnectionString = xlsconStr;
                break;

            case ".xlsx":
            case ".xlsm":
                string xlsxconStr = @"Provider=Microsoft.ACE.OLEDB.12.0;Data Source='" + openFileDialog1.FileName + "'; Extended Properties=Excel 12.0;";
                con.ConnectionString = xlsxconStr;
                break;
        }
            using (System.Data.OleDb.OleDbCommand oconn = new System.Data.OleDb.OleDbCommand("SELECT * FROM [" + listBox1.SelectedIndex.ToString() + "$]", con))
            {
                con.Open();

                System.Data.OleDb.OleDbDataAdapter adapter = new System.Data.OleDb.OleDbDataAdapter(oconn);
                System.Data.DataTable data = new System.Data.DataTable();
                adapter.Fill(data);
                dataGridView1.DataSource = data;
            }
    }

现在您的代码将输入 switch case 语句以初始化您的连接字符串；）

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