Subquery.Take

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

@@ -0,0 +1,93 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Linq.Expressions;
+using System.Text;
+
+namespace SqlSugar
+{
+    public class SubTake : ISubOperation
+    {
+        public bool HasWhere
+        {
+            get; set;
+        }
+
+        public ExpressionContext Context
+        {
+            get; set;
+        }
+
+        public Expression Expression
+        {
+            get; set;
+        }
+
+        public string Name
+        {
+            get
+            {
+                return "Take";
+            }
+        }
+
+        public int Sort
+        {
+            get
+            {
+                if (this.Context is SqlServerExpressionContext || this.Context.GetType().Name.Contains("Access"))
+                {
+                    return 150;
+                }
+                else if (this.Context is OracleExpressionContext)
+                {
+
+                    return 401;
+                }
+                else
+                {
+                    return 490;
+                }
+            }
+        }
+
+
+        public string GetValue(Expression expression)
+        {
+            var numExp = (expression as MethodCallExpression).Arguments[0];
+            var num =1;
+            if (ExpressionTool.GetParameters(numExp).Any()) 
+            { 
+                var copyContext = this.Context.GetCopyContextWithMapping();
+                copyContext.IsSingle = false;
+                copyContext.Resolve(numExp, ResolveExpressType.WhereMultiple);
+                copyContext.Result.GetString();
+            }
+            else 
+            {
+                num = ExpressionTool.DynamicInvoke(numExp).ObjToInt();
+            }
+            var take = (expression as MethodCallExpression); 
+            if (this.Context is SqlServerExpressionContext || this.Context.GetType().Name.Contains("Access"))
+            {
+                return "TOP " + num;
+            }
+            else if (this.Context is OracleExpressionContext)
+            {
+                return (HasWhere ? "AND" : "WHERE") + " ROWNUM<=" + num;
+            }
+            else if (this.Context is PostgreSQLExpressionContext || this.Context?.SugarContext?.Context?.CurrentConnectionConfig?.MoreSettings?.DatabaseModel == DbType.PostgreSQL)
+            {
+                return "limit " + num;
+            }
+            else if (this.Context.GetLimit() != null)
+            {
+                return this.Context.GetLimit();
+            }
+            else
+            {
+                return "limit " + num;
+            }
+        }
+    }
+}

Src/Asp.NetCore2/SqlSugar/ExpressionsToSql/Subquery/SubTools.cs

@@ -40,7 +40,8 @@ namespace SqlSugar
                                                     new SubDistinctCount{ Context=Context },
                                                     new SubToList{ Context=Context},
                                                     new SubFirst(){ Context=Context },
-                                                    new SubAsWithAttr(){ Context=Context }
+                                                    new SubAsWithAttr(){ Context=Context },
+                                                    new SubTake(){ Context=Context }
                                                 };
         }
 

Src/Asp.NetCore2/SqlSugar/ExpressionsToSql/Subquery/Subquerable.cs

@@ -224,5 +224,10 @@ namespace SqlSugar
         {
             return this;
         }
+
+        public Subqueryable<T> Take(int takeNum)
+        {
+            return this;
+        }
     }
 }