public enum DatabaseType
{
    SqlServer,   // SQL Server
    MySQL,       // MySQL
    PostgreSQL,  // PostgreSQL
    Oracle       // Oracle（預(yù)留）
}

// 列信息
public class ColumnInfo
{
    public string TableName { get; set; }    // 表名
    public string ColumnName { get; set; }   // 列名
    public string DataType { get; set; }     // 數(shù)據(jù)類型（如int、nvarchar(50)）
    public int MaxLength { get; set; }       // 最大長度
    public bool IsNullable { get; set; }     // 是否允許NULL
    public string DefaultValue { get; set; } // 默認(rèn)值
    public int OrdinalPosition { get; set; }  // 列順序
}
// 主鍵信息
public class PrimaryKeyInfo
{
    public string TableName { get; set; }
    public string ColumnName { get; set; }
    public int KeyOrder { get; set; }  // 主鍵順序（復(fù)合主鍵）
}
// 表結(jié)構(gòu)匯總
public class TableSchema
{
    public string TableName { get; set; }
    public List<ColumnInfo> Columns { get; set; } = new();
    public List<PrimaryKeyInfo> PrimaryKeys { get; set; } = new();
}

using System.Data.Common;
using Microsoft.Data.SqlClient;  // SQL Server驅(qū)動
using MySqlConnector;            // MySQL驅(qū)動
public class DbSchemaReader
{
    private readonly string _connectionString;
    private readonly DatabaseType _dbType;
    public DbSchemaReader(string connectionString, DatabaseType dbType)
    {
        _connectionString = connectionString;
        _dbType = dbType;
    }
    // 創(chuàng)建數(shù)據(jù)庫連接
    private DbConnection CreateConnection()
    {
        return _dbType switch
        {
            DatabaseType.SqlServer => new SqlConnection(_connectionString),
            DatabaseType.MySQL => new MySqlConnection(_connectionString),
            _ => throw new NotSupportedException($"不支持的數(shù)據(jù)庫類型: {_dbType}")
        };
    }
    // 執(zhí)行查詢并返回DataTable
    public DataTable ExecuteQuery(string sql)
    {
        using var conn = CreateConnection();
        conn.Open();
        using var cmd = conn.CreateCommand();
        cmd.CommandText = sql;
        using var adapter = GetDataAdapter(cmd);
        var dt = new DataTable();
        adapter.Fill(dt);
        return dt;
    }
    // 獲取數(shù)據(jù)庫適配器（適配不同數(shù)據(jù)庫）
    private DbDataAdapter GetDataAdapter(DbCommand cmd)
    {
        return _dbType switch
        {
            DatabaseType.SqlServer => new SqlDataAdapter((SqlCommand)cmd),
            DatabaseType.MySQL => new MySqlDataAdapter((MySqlCommand)cmd),
            _ => throw new NotSupportedException()
        };
    }
}

// 獲取指定表的所有列信息
public List<ColumnInfo> GetColumns(string tableName)
{
    string sql = @"
        SELECT 
            c.TABLE_NAME AS TableName,
            c.COLUMN_NAME AS ColumnName,
            c.DATA_TYPE AS DataType,
            c.CHARACTER_MAXIMUM_LENGTH AS MaxLength,
            CASE WHEN c.IS_NULLABLE = 'YES' THEN 1 ELSE 0 END AS IsNullable,
            c.COLUMN_DEFAULT AS DefaultValue,
            c.ORDINAL_POSITION AS OrdinalPosition
        FROM INFORMATION_SCHEMA.COLUMNS c
        WHERE c.TABLE_NAME = @TableName
        ORDER BY c.ORDINAL_POSITION";
    using var conn = CreateConnection();
    conn.Open();
    using var cmd = conn.CreateCommand();
    cmd.CommandText = sql;
    cmd.Parameters.Add(new SqlParameter("@TableName", tableName));
    using var reader = cmd.ExecuteReader();
    var columns = new List<ColumnInfo>();
    while (reader.Read())
    {
        columns.Add(new ColumnInfo
        {
            TableName = reader["TableName"].ToString(),
            ColumnName = reader["ColumnName"].ToString(),
            DataType = reader["DataType"].ToString(),
            MaxLength = reader["MaxLength"] == DBNull.Value ? 0 : Convert.ToInt32(reader["MaxLength"]),
            IsNullable = Convert.ToBoolean(reader["IsNullable"]),
            DefaultValue = reader["DefaultValue"]?.ToString(),
            OrdinalPosition = Convert.ToInt32(reader["OrdinalPosition"])
        });
    }
    return columns;
}

// 獲取指定表的主鍵列
public List<PrimaryKeyInfo> GetPrimaryKeys(string tableName)
{
    string sql = @"
        SELECT 
            kcu.TABLE_NAME AS TableName,
            kcu.COLUMN_NAME AS ColumnName,
            kcu.ORDINAL_POSITION AS KeyOrder
        FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE kcu
        JOIN INFORMATION_SCHEMA.TABLE_CONSTRAINTS tc 
            ON kcu.CONSTRAINT_NAME = tc.CONSTRAINT_NAME
        WHERE tc.TABLE_NAME = @TableName 
            AND tc.CONSTRAINT_TYPE = 'PRIMARY KEY'
        ORDER BY kcu.ORDINAL_POSITION";
    // 執(zhí)行查詢（類似GetColumns方法，略）
    // ...
}

// 獲取指定表的所有結(jié)構(gòu)信息
public TableSchema GetTableSchema(string tableName)
{
    var schema = new TableSchema { TableName = tableName };
    schema.Columns = GetColumns(tableName);
    schema.PrimaryKeys = GetPrimaryKeys(tableName);
    return schema;
}

// 序列化為JSON
var json = JsonSerializer.Serialize(schema, new JsonSerializerOptions { WriteIndented = true });
// 生成HTML表格
string html = $"<h1>{schema.TableName} 結(jié)構(gòu)</h1><table border='1'>...";

// 生成實體類代碼
string GenerateEntityClass(TableSchema schema)
{
    var sb = new StringBuilder();
    sb.AppendLine($"public class {schema.TableName}");
    sb.AppendLine("{");
    foreach (var col in schema.Columns)
    {
        string type = MapDbTypeToCSharp(col.DataType);
        sb.AppendLine($"    public {type} {col.ColumnName} {{ get; set; }}");
    }
    sb.AppendLine("}");
    return sb.ToString();
}
// 數(shù)據(jù)庫類型映射C#類型
private string MapDbTypeToCSharp(string dbType)
{
    return dbType.ToLower() switch
    {
        "int" => "int",
        "nvarchar" => "string",
        "datetime" => "DateTime",
        _ => "object"
    };
}