Where(conditionals)

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

@@ -432,7 +432,7 @@ 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.Net/SqlSugar/Abstract/SqlBuilderProvider/SqlBuilderProvider.cs

@@ -164,8 +164,19 @@ namespace SqlSugar
                     switch (item.ConditionalType)
                     {
                         case ConditionalType.Equal:
-                            builder.AppendFormat(temp, type, item.FieldName.ToSqlFilter(), "=", parameterName);
-                            parameters.Add(new SugarParameter(parameterName, GetFieldValue(item)));
+                            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);