Add Subquery.First()

Src/Asp.Net/SqlSugar/Abstract/QueryableProvider/QueryableHelper.cs

@@ -1693,7 +1693,13 @@ namespace SqlSugar
         {
             var ps = this.QueryBuilder.Parameters;
             var itemProperty = typeof(TResult).GetProperty(subPara.Key);
-            var callType = itemProperty.PropertyType.GetGenericArguments()[0];
+            var callType = itemProperty.PropertyType.GetGenericArguments().FirstOrDefault();
+            var isFirst = false;
+            if (callType == null) 
+            {
+                callType = itemProperty.PropertyType;
+                isFirst = true;
+            }
             var sql = subPara.Value.ObjToString().Replace("@sugarIndex", "0");
             sql =SqlBuilder.RemoveParentheses(sql);
             var methodParamters = new object[] { sql, ps };
@@ -1711,7 +1717,14 @@ namespace SqlSugar
                 }
                 else
                 {
-                    itemProperty.SetValue(item, subList);
+                    if (isFirst)
+                    {
+                        itemProperty.SetValue(item, (subList as IList)[0] );
+                    }
+                    else
+                    {
+                        itemProperty.SetValue(item, subList);
+                    }
                 }
             }
         }
@@ -1741,10 +1754,14 @@ namespace SqlSugar
 
                 index++;
             }
-
             var itemProperty = typeof(TResult).GetProperty(subPara.Key);
-            var callType = itemProperty.PropertyType.GetGenericArguments()[0];
-
+            var callType = itemProperty.PropertyType.GetGenericArguments().FirstOrDefault();
+            var isFirst = false;
+            if (callType == null)
+            {
+                callType = itemProperty.PropertyType;
+                isFirst = true;
+            }
             var sqlstring = string.Join(" \r\n UNION ALL  ", sqls);
             var methodParamters = new object[] { sqlstring, ps.ToArray() };
             this.QueryBuilder.SubToListParameters = null;
@@ -1755,7 +1772,11 @@ namespace SqlSugar
             var subList = ExpressionBuilderHelper.CallFunc(callType, methodParamters, this.Clone(), "SubQueryList");
             var appendValue = this.QueryBuilder.AppendValues;
             var list = (subList as IEnumerable).Cast<object>().ToList();
-            if (typeof(TResult).IsAnonymousType())
+            if (isFirst) 
+            {
+                SetSubListWithClassFirst(result, itemProperty, appendValue, list, 0);
+            }
+            else if (typeof(TResult).IsAnonymousType())
             {
                 SetSubListWithAnonymousType(result, itemProperty, appendValue, list, 0);
             }
@@ -1791,6 +1812,30 @@ namespace SqlSugar
             }
             return resIndex;
         }
+        private static int SetSubListWithClassFirst<TResult>(List<TResult> result, PropertyInfo itemProperty, List<List<QueryableAppendColumn>> appendValue, List<object> list, int resIndex)
+        {
+            foreach (var item in result)
+            {
+                //var setValue = Activator.CreateInstance(itemProperty.PropertyType, true);
+                if (appendValue != null)
+                {
+                    var appindex = 0;
+                    foreach (var appValue in appendValue)
+                    {
+                        if (appValue[0].Value.ObjToInt() == resIndex)
+                        {
+                            var addItem = list[appindex];
+                            itemProperty.SetValue(item, addItem);
+                        }
+                        appindex++;
+                    }
+                }
+                //itemProperty.SetValue(item, setValue);
+                resIndex++;
+            }
+
+            return resIndex;
+        }
 
         private static int SetSubListWithClass<TResult>(List<TResult> result, PropertyInfo itemProperty, List<List<QueryableAppendColumn>> appendValue, List<object> list, int resIndex)
         {

Src/Asp.Net/SqlSugar/ExpressionsToSql/ResolveItems/BaseResolve_Validate.cs

@@ -14,7 +14,7 @@ namespace SqlSugar
 
         private static bool IsSubToList(Expression item)
         {
-            return ExpressionTool.GetMethodName(item) == "ToList" && IsSubquery(item);
+            return ExpressionTool.GetMethodName(item).IsIn("ToList","First") && IsSubquery(item);
         }
 
         private static bool IsSubquery(Expression item)

Src/Asp.Net/SqlSugar/ExpressionsToSql/Subquery/Items/SubFirst.cs

@@ -0,0 +1,124 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Linq.Expressions;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace SqlSugar 
+{
+    public class SubFirst : ISubOperation
+    {
+        public bool HasWhere
+        {
+            get; set;
+        }
+
+        public string Name
+        {
+            get
+            {
+                return "First";
+            }
+        }
+
+        public Expression Expression
+        {
+            get; set;
+        }
+
+
+        public int Sort
+        {
+            get
+            {
+                return 200;
+            }
+        }
+
+        public ExpressionContext Context
+        {
+            get; set;
+        }
+
+        public string GetValue(Expression expression = null)
+        {
+            ;
+            var exp = expression as MethodCallExpression;
+            InitType(exp);
+            var type = expression.Type;
+            if (type.FullName.IsCollectionsList()
+                && exp.Arguments.Count == 0 && type.GenericTypeArguments.Length > 0
+                && this.Context.SugarContext != null
+                && this.Context.SugarContext.QueryBuilder.IsSelectNoAll)
+            {
+                var entity = type.GenericTypeArguments[0];
+                var columnNames = this.Context.SugarContext.Context.EntityMaintenance.GetEntityInfo(entity).Columns;
+                var columnsString = string.Join(",", columnNames
+                    .Where(it => it.IsIgnore == false)
+                    .Where(it => it.DbColumnName.HasValue())
+                    .Select(it => this.Context.GetTranslationColumnName(it.DbColumnName)));
+                return $"{columnsString},@sugarIndex as sugarIndex";
+            }
+            else if (exp.Arguments.Count == 0)
+            {
+                return "*,@sugarIndex as sugarIndex";
+            }
+            var argExp = exp.Arguments[0];
+            var parametres = (argExp as LambdaExpression).Parameters;
+            if ((argExp as LambdaExpression).Body is UnaryExpression)
+            {
+                argExp = ((argExp as LambdaExpression).Body as UnaryExpression).Operand;
+            }
+            var argLambda = argExp as LambdaExpression;
+            var copyContext = this.Context.GetCopyContextWithMapping();
+            copyContext.Resolve(argLambda, ResolveExpressType.SelectMultiple);
+            var select = copyContext.Result.GetString();
+            this.Context.Parameters.AddRange(copyContext.Parameters);
+            this.Context.Index = copyContext.Index;
+            this.Context.ParameterIndex = copyContext.ParameterIndex;
+            SetShortName(exp, null);
+            return select + ",@sugarIndex as sugarIndex";
+        }
+
+        private void InitType(MethodCallExpression exp)
+        {
+            if (exp.Arguments.Count > 0)
+            {
+                foreach (var arg in (exp.Arguments[0] as LambdaExpression).Parameters)
+                {
+                    if (this.Context.InitMappingInfo != null)
+                    {
+                        this.Context.InitMappingInfo(arg.Type);
+                        this.Context.RefreshMapping();
+                    }
+                }
+            }
+        }
+
+        public void SetShortName(MethodCallExpression exp, string result)
+        {
+            if (exp.Arguments[0] is LambdaExpression)
+            {
+                var parameters = (exp.Arguments[0] as LambdaExpression).Parameters;
+                if (parameters != null && parameters.Count > 0)
+                {
+                    this.Context.CurrentShortName = this.Context.GetTranslationColumnName(parameters[0].ObjToString());
+                }
+
+            }
+        }
+        public void SetShortNameNext(MethodCallExpression exp, string result)
+        {
+            if (exp.Arguments.Count > 1 && exp.Arguments[1] is LambdaExpression)
+            {
+                var parameters = (exp.Arguments[1] as LambdaExpression).Parameters;
+                if (parameters != null && parameters.Count > 0)
+                {
+                    this.Context.CurrentShortName = this.Context.GetTranslationColumnName(parameters[0].ObjToString());
+                }
+
+            }
+        }
+    }
+}

Src/Asp.Net/SqlSugar/ExpressionsToSql/Subquery/SubResolve.cs

@@ -223,7 +223,7 @@ namespace SqlSugar
             }).ToList();
             SetOrderByIndex(isubList);
             isubList.Insert(0, new SubBegin());
-            if (isubList.Any(it => it is SubSelect))
+            if (isubList.Any(it => it is SubSelect||it is SubFirst))
             {
                 isubList.Add(new SubTop() { Context = this.context });
             }

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

@@ -38,7 +38,8 @@ namespace SqlSugar
                                                     new SubEnableTableFilter(){ Context=Context },
                                                     new SubSelectStringJoin{ Context=Context },
                                                     new SubDistinctCount{ Context=Context },
-                                                    new SubToList{ Context=Context}
+                                                    new SubToList{ Context=Context},
+                                                    new SubFirst(){ Context=Context }
                                                 };
         }
 

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

@@ -180,5 +180,10 @@ namespace SqlSugar
         {
             return null;
         }
+
+        public T First()
+        {
+            return default(T);
+        }
     }
 }

Src/Asp.Net/SqlSugar/SqlSugar.csproj

@@ -154,6 +154,7 @@
     <Compile Include="ExpressionsToSql\ResolveItems\MethodCallExpressionResolve_Helper.cs" />
     <Compile Include="ExpressionsToSql\ResolveItems\MethodCallExpressionResolve_BaseDateFomat.cs" />
     <Compile Include="ExpressionsToSql\Subquery\Items\SubDistinctCount.cs" />
+    <Compile Include="ExpressionsToSql\Subquery\Items\SubFirst.cs" />
     <Compile Include="ExpressionsToSql\Subquery\Items\SubSelectStringJoin.cs" />
     <Compile Include="ExpressionsToSql\Subquery\Items\SubToList.cs" />
     <Compile Include="ExpressionsToSql\Subquery\Items\SubWithNoLock.cs" />