GetSchemaTable()不返回IsKey属性

Question

-Hello，世界！-

我正在做一个C#和ASP.NET项目，我遇到了一个麻烦。该项目将动态地从表中加载元数据和记录，以编辑这些元数据和记录，而无需静态地定义可以编辑哪些表。因此，我需要获得不同表的模式/元数据。

到目前为止，我的情况如下：

// initialize the connection
using (SqlConnection con = new SqlConnection(metadata.DatabaseString))
{
    // open the connection
    con.Open();

    // initialize a new SqlCommand to get the schema
    SqlCommand command = con.CreateCommand();
    command.CommandType = CommandType.Text;

    // 0 = 1 ensures it's always an empty data set
    command.CommandText = "SELECT * FROM " + metadata.TableName + " WHERE 0=1;";

    // set to SchemaOnly to improve performance (i think)
    SqlDataReader reader = command.ExecuteReader(CommandBehavior.SchemaOnly);

    // GetSchemaTable() gets the table's metadata
    DataTable dataTable = reader.GetSchemaTable();

    // loops through all the rows of the data table
    foreach (DataRow row in dataTable.Rows)
    {
        // field names found here: https://msdn.microsoft.com/en-us/library/system.data.datatablereader.getschematable(v=vs.110).aspx#Remarks
        metadata.ColumnMetadata.Add(new ColumnWrapper()
        {
            ColumnType = GetTypeFromSql(row.Field<string>("DataTypeName")),
            ColumnRawType = row.Field<string>("DataTypeName"),
            ColumnName = row.Field<string>("ColumnName"),
            ByteSize = row.Field<int>("ColumnSize"),
            IsKey = row.Field<bool?>("IsKey") ?? false
        });
    }
}

问题是IsKey字段总是空的。使用以下查询创建了我的Server表：

CREATE TABLE [dbo].[Dtm_LKUP_Role] (
    [DtmRoleId] INT IDENTITY (1, 1) NOT NULL,
    [RoleName]  VARCHAR(32) NOT NULL,
    [IsActive]  BIT DEFAULT ((1)) NOT NULL,
    PRIMARY KEY CLUSTERED ([DtmRoleId] ASC)
);

以下是我迄今尝试过的：

• 使用不同的表，结果相同
• 接入dataTable.Columns["IsKey"]

无论我在哪里看，我都找不到我需要的信息。有谁知道是什么原因造成的吗？如果与此相关，我将使用MDF文件和LocalDB来连接数据库，而不是使用活动服务器。

Answer 1

休斯敦，我们起飞了！

基于mjwills的帮助，我将代码更改为：

// initialize the connection
using (SqlConnection con = new SqlConnection(metadata.DatabaseString))
{
    // open the connection
    con.Open();

    // initialize a new SqlCommand to get the schema. 0 = 1 ensures an empty data set
    SqlDataAdapter adapter = new SqlDataAdapter("SELECT * FROM " + metadata.TableName + " WHERE 0=1", con);

    // GetSchemaTable() gets the table's metadata
    DataTable dataTable = new DataTable();

    // tell the adapater to fill in the missing schema
    adapter.MissingSchemaAction = MissingSchemaAction.AddWithKey;

    // fill the datatable with the schema
    adapter.FillSchema(dataTable, SchemaType.Mapped);

    // loops through all the rows of the data table
    foreach (DataColumn column in dataTable.Columns)
    {
        // field names found here: https://msdn.microsoft.com/en-us/library/system.data.datatablereader.getschematable(v=vs.110).aspx#Remarks
        metadata.ColumnMetadata.Add(new ColumnWrapper()
        {
            ColumnType = column.DataType,
            ColumnName = column.ColumnName,
            ByteSize = column.MaxLength,
            IsKey = dataTable.PrimaryKey.Contains(column)
        });
    }
}

我很感谢那些对我原来的问题发表评论的人的帮助:)