Question

我是新手，我正在尝试从我的数据库中的某些表中检索Column NAme，Size（max legth）和DataType，当我执行它时，以下代码期望它显示所有列类型和名称（i没有找到如何引用Size，我使用了ColumnSize，但据说DataColumn不包含此方法的定义）但在执行时，它只显示：IsColumnSetSystem.Boolean 这是代码：

private void button1_Click(object sender, EventArgs e)
    {
        string EF = textBox1.Text;

        try{
            //SqlDataAdapter adapter = SetupDataAdapter("SELECT * FROM id_declarant");
     SqlCommand comm = new SqlCommand();
     string connectionString = @"Data Source=.\SQLEXPRESS;Initial Catalog=declaration;Integrated Security=True";
      comm.Connection=new SqlConnection(connectionString);
            String sql = @"SELECT * 
                  FROM id_declarant,declarant
                 WHERE (declarant.Nom_pren_RS='" + EF + "') and (id_declarant.mat_fisc=declarant.mat_fisc)  "; 
     comm.CommandText = sql;
  comm.Connection.Open();
             SqlDataReader reader = comm.ExecuteReader();
             DataTable schemaTable = reader.GetSchemaTable();
             foreach (DataRow row in schemaTable.Rows)
             {
                 foreach (DataColumn column in schemaTable.Columns)
                 {
                     System.IO.File.WriteAllText(@"C:\Users\Manuela\Documents\GL4\WriteLines.txt", column.ColumnName + column.DataType );

                 }
             }

Answer 1

也许我对这个有点偏僻但要获得列的名称，大小和数据类型，你可以试试这个：

DataTable schemaTable = reader.GetSchemaTable();
foreach (DataRow row in schemaTable.Rows)
{
    var name = row["ColumnName"];
    var size = row["ColumnSize"];
    var dataType = row["DataTypeName"];
    //append these to a string or StringBuilder for writing out later...
}

但也许这不是你想要的？

Answer 2

您正在打印GetSchemaTable返回的数据表的列名，而不是其值，我建议使用StringBuilder并在退出循环时写入所有内容

    StringBuilder sb = new StringBuilder();
    foreach (DataRow row in schemaTable.Rows)
    {
        foreach (DataColumn column in schemaTable.Columns)
        {
            sb.AppendLine(column.ColumnName + ":"  +row[column.ColumnName].ToString());
        }
        sb.AppendLine();
    }
    File.WriteAllText(@"C:\Users\Manuela\Documents\GL4\WriteLines.txt", sb.ToString());

我们如何从getschemaTable获取Column Size和dataType？

2 个答案: