Update .net core project

Src/Asp.NetCore2/SqlSugar/Abstract/QueryableProvider/QueryableProvider.cs

@@ -419,6 +419,10 @@ namespace SqlSugar
             }
             return this;
         }
+        public ISugarQueryable<T> WhereColumns(Dictionary<string, object>  dictionary) 
+        {
+            return WhereColumns(new List<Dictionary<string, object>> { dictionary });
+        }
         public ISugarQueryable<T> WhereColumns(List<Dictionary<string, object>> list)
         {
             List<IConditionalModel> conditionalModels = new List<IConditionalModel>();
@@ -432,7 +436,7 @@ namespace SqlSugar
                     {
                         FieldName = item,
                         ConditionalType = ConditionalType.Equal,
-                        FieldValue = model[item].ObjToString(),
+                        FieldValue = model[item]==null?"null" : model[item].ObjToString(),
                         CSharpTypeName = model[item] == null ? null : model[item].GetType().Name
                     }));
                     i++;

Src/Asp.NetCore2/SqlSugar/Abstract/SaveableProvider/Storageable.cs

@@ -331,7 +331,7 @@ namespace SqlSugar
                         FieldName = item.DbColumnName,
                         ConditionalType = ConditionalType.Equal,
                         CSharpTypeName=UtilMethods.GetTypeName(value),
-                        FieldValue = value + "",
+                        FieldValue = value==null?"null":value.ObjToString(),
                         FieldValueConvertFunc=this.Context.CurrentConnectionConfig.DbType==DbType.PostgreSQL? 
                                                UtilMethods.GetTypeConvert(value):null
                     }));

Src/Asp.NetCore2/SqlSugar/Abstract/SqlBuilderProvider/SqlBuilderProvider.cs

@@ -164,8 +164,19 @@ namespace SqlSugar
                     switch (item.ConditionalType)
                     {
                         case ConditionalType.Equal:
+                            if (item.FieldValue!=null&&item.FieldValue == "null"&&item.FieldValue!= "[null]")
+                            {
+                                builder.AppendFormat($" {item.FieldName.ToSqlFilter()} is null ");
+                            }
+                            else
+                            {
+                                if (item.FieldValue == "[null]") 
+                                {
+                                    item.FieldValue = "null";
+                                }
                                 builder.AppendFormat(temp, type, item.FieldName.ToSqlFilter(), "=", parameterName);
                                 parameters.Add(new SugarParameter(parameterName, GetFieldValue(item)));
+                            }
                             break;
                         case ConditionalType.Like:
                             builder.AppendFormat(temp, type, item.FieldName.ToSqlFilter(), "LIKE", parameterName);

Src/Asp.NetCore2/SqlSugar/Interface/IQueryable.cs

@@ -54,6 +54,7 @@ namespace SqlSugar
         ISugarQueryable<T> WhereClassByPrimaryKey(List<T> list);
         ISugarQueryable<T> WhereClassByPrimaryKey(T data) ;
         ISugarQueryable<T> WhereColumns(List<Dictionary<string, object>> columns);
+        ISugarQueryable<T> WhereColumns(Dictionary<string, object> columns);
         ISugarQueryable<T> TranLock(DbLockType LockType = DbLockType.Wait);
         ISugarQueryable<T> Where(Expression<Func<T, bool>> expression);
         ISugarQueryable<T> Where(string whereString, object parameters = null);

Src/Asp.NetCore2/SqlSugar/Realization/MySql/SqlBuilder/MySqlBlukCopy.cs

@@ -176,6 +176,10 @@ namespace SqlSugar
                     {
                         sb.Append(row[colum].ObjToDate().ToString("yyyy-MM-dd HH:mm:ss.fff"));
                     }
+                    else if (colum.DataType == UtilConstants.DateType && row[colum] != null && row[colum] == DBNull.Value)
+                    {
+                        sb.Append("NULL");
+                    }
                     else sb.Append(row[colum].ToString());
                 }
                 sb.AppendLine();