Update exp to sql

Src/Asp.NetCore2/SqlSugar/ExpressionsToSql/DbMethods/DefaultDbMethod.cs

@@ -9,6 +9,7 @@ namespace SqlSugar
 {
     public partial class DefaultDbMethod : IDbMethods
     {
+        public ISqlSugarClient sqlSugarClient { get; set; }
         public virtual string ParameterKeyWord { get; set; }= "@";
         public virtual string RowNumber(MethodCallExpressionModel model) 
         {

Src/Asp.NetCore2/SqlSugar/ExpressionsToSql/DbMethods/IDbMethods.cs

@@ -11,6 +11,7 @@ namespace SqlSugar
 {
     public interface IDbMethods
     {
+        ISqlSugarClient sqlSugarClient { get; set; }
         string IIF(MethodCallExpressionModel model);
         string HasNumber(MethodCallExpressionModel model);
         string HasValue(MethodCallExpressionModel model);

Src/Asp.NetCore2/SqlSugar/ExpressionsToSql/Subquery/Items/SubSelectStringJoin.cs

@@ -65,6 +65,7 @@ namespace SqlSugar
                     result =  string.Join(",",(constant.Value+"").Split(',').Select(it=>this.Context.GetTranslationTableName(it)));
                 }
             }
+            this.Context.DbMehtods.sqlSugarClient = this.Context?.SugarContext?.Context;
             result = this.Context.DbMehtods.GetStringJoinSelector(result, ExpressionTool.GetExpressionValue(exp.Arguments[1]) + "");
 
             return result;