## v0.9.17 (ODBC)

- 增加 FreeSql.Provider.Odbc，实现 Oracle/SqlServer/MySql 的 Odbc 访问提供；
- 增加 FreeSqlBuilder.UseConnectionString 参数 providerType，可解决因包版本冲突时，可能无法反射获得 FreeSql.Provider 对应的类型，通常这个参数不需要设置；
- 优化 MaxLength 特性，当指定为 -1 时 DbType 会分别映射类型 text/nvarchar(max)/nvarchar2(4000)；

Providers/FreeSql.Provider.Odbc/Oracle/OdbcOracleAdo/OdbcOracleAdo.cs

@@ -0,0 +1,70 @@
+using FreeSql.Internal;
+using SafeObjectPool;
+using System;
+using System.Collections;
+using System.Data.Common;
+using System.Data.Odbc;
+using System.Text;
+using System.Threading;
+
+namespace FreeSql.Odbc.Oracle
+{
+    class OdbcOracleAdo : FreeSql.Internal.CommonProvider.AdoProvider
+    {
+        public OdbcOracleAdo() : base(DataType.Oracle) { }
+        public OdbcOracleAdo(CommonUtils util, string masterConnectionString, string[] slaveConnectionStrings) : base(DataType.Oracle)
+        {
+            base._util = util;
+            if (!string.IsNullOrEmpty(masterConnectionString))
+                MasterPool = new OdbcOracleConnectionPool("主库", masterConnectionString, null, null);
+            if (slaveConnectionStrings != null)
+            {
+                foreach (var slaveConnectionString in slaveConnectionStrings)
+                {
+                    var slavePool = new OdbcOracleConnectionPool($"从库{SlavePools.Count + 1}", slaveConnectionString, () => Interlocked.Decrement(ref slaveUnavailables), () => Interlocked.Increment(ref slaveUnavailables));
+                    SlavePools.Add(slavePool);
+                }
+            }
+        }
+        static DateTime dt1970 = new DateTime(1970, 1, 1);
+        public override object AddslashesProcessParam(object param, Type mapType)
+        {
+            if (param == null) return "NULL";
+            if (mapType != null && mapType != param.GetType())
+                param = Utils.GetDataReaderValue(mapType, param);
+            if (param is bool || param is bool?)
+                return (bool)param ? 1 : 0;
+            else if (param is string || param is char)
+                return string.Concat("'", param.ToString().Replace("'", "''"), "'");
+            else if (param is Enum)
+                return ((Enum)param).ToInt64();
+            else if (decimal.TryParse(string.Concat(param), out var trydec))
+                return param;
+            else if (param is DateTime || param is DateTime?)
+                return string.Concat("to_timestamp('", ((DateTime)param).ToString("yyyy-MM-dd HH:mm:ss.ffffff"), "','YYYY-MM-DD HH24:MI:SS.FF6')");
+            else if (param is TimeSpan || param is TimeSpan?)
+                return $"numtodsinterval({((TimeSpan)param).Ticks * 1.0 / 10000000},'second')";
+            else if (param is IEnumerable)
+            {
+                var sb = new StringBuilder();
+                var ie = param as IEnumerable;
+                foreach (var z in ie) sb.Append(",").Append(AddslashesProcessParam(z, mapType));
+                return sb.Length == 0 ? "(NULL)" : sb.Remove(0, 1).Insert(0, "(").Append(")").ToString();
+            }
+            return string.Concat("'", param.ToString().Replace("'", "''"), "'");
+            //if (param is string) return string.Concat('N', nparms[a]);
+        }
+
+        protected override DbCommand CreateCommand()
+        {
+            return new OdbcCommand();
+        }
+
+        protected override void ReturnConnection(ObjectPool<DbConnection> pool, Object<DbConnection> conn, Exception ex)
+        {
+            (pool as OdbcOracleConnectionPool).Return(conn, ex);
+        }
+
+        protected override DbParameter[] GetDbParamtersByObject(string sql, object obj) => _util.GetDbParamtersByObject(sql, obj);
+    }
+}