diff --git a/SQLBuilder.Core/Extensions.cs b/SQLBuilder.Core/Extensions.cs
index e547ffd..02b806d 100644
--- a/SQLBuilder.Core/Extensions.cs
+++ b/SQLBuilder.Core/Extensions.cs
@@ -312,6 +312,30 @@ public static bool IsNull(this object @this)
         }
         #endregion
 
+        #region IsNullOrEmpty
+        /// <summary>
+        /// 判断字符串是否为空
+        /// </summary>
+        /// <param name="this">待验证的字符串</param>
+        /// <returns>bool</returns>
+        public static bool IsNullOrEmpty(this string @this)
+        {
+            return string.IsNullOrEmpty(@this);
+        }
+        #endregion
+
+        #region IsNullOrWhiteSpace
+        /// <summary>
+        /// 判断字符串是否为空
+        /// </summary>
+        /// <param name="this">待验证的字符串</param>
+        /// <returns>bool</returns>
+        public static bool IsNullOrWhiteSpace(this string @this)
+        {
+            return string.IsNullOrWhiteSpace(@this);
+        }
+        #endregion
+
         #region ToSafeValue
         /// <summary>
         /// 转换为安全类型的值
diff --git a/SQLBuilder.Core/Repositories/MySqlRepository.cs b/SQLBuilder.Core/Repositories/MySqlRepository.cs
index aa33689..2c5c06e 100644
--- a/SQLBuilder.Core/Repositories/MySqlRepository.cs
+++ b/SQLBuilder.Core/Repositories/MySqlRepository.cs
@@ -70,6 +70,11 @@ public DbConnection Connection
                     if (_dbConnection.State != ConnectionState.Open)
                         _dbConnection.Open();
                 }
+                //DbConnection被using后连接字符串被置为空
+                else if (_dbConnection.ConnectionString.IsNullOrEmpty())
+                {
+                    _dbConnection.ConnectionString = ConnectionString;
+                }
                 return _dbConnection;
             }
             set
diff --git a/SQLBuilder.Core/Repositories/NpgsqlRepository.cs b/SQLBuilder.Core/Repositories/NpgsqlRepository.cs
index edbf1d6..0f29a44 100644
--- a/SQLBuilder.Core/Repositories/NpgsqlRepository.cs
+++ b/SQLBuilder.Core/Repositories/NpgsqlRepository.cs
@@ -70,6 +70,11 @@ public DbConnection Connection
                     if (_dbConnection.State != ConnectionState.Open)
                         _dbConnection.Open();
                 }
+                //DbConnection被using后连接字符串被置为空
+                else if (_dbConnection.ConnectionString.IsNullOrEmpty())
+                {
+                    _dbConnection.ConnectionString = ConnectionString;
+                }
                 return _dbConnection;
             }
             set
diff --git a/SQLBuilder.Core/Repositories/OracleRepository.cs b/SQLBuilder.Core/Repositories/OracleRepository.cs
index 589c5ea..56ad4d4 100644
--- a/SQLBuilder.Core/Repositories/OracleRepository.cs
+++ b/SQLBuilder.Core/Repositories/OracleRepository.cs
@@ -70,6 +70,11 @@ public DbConnection Connection
                     if (_dbConnection.State != ConnectionState.Open)
                         _dbConnection.Open();
                 }
+                //DbConnection被using后连接字符串被置为空
+                else if (_dbConnection.ConnectionString.IsNullOrEmpty())
+                {
+                    _dbConnection.ConnectionString = ConnectionString;
+                }
                 return _dbConnection;
             }
             set
diff --git a/SQLBuilder.Core/Repositories/SqlRepository.cs b/SQLBuilder.Core/Repositories/SqlRepository.cs
index bb372dd..338f0af 100644
--- a/SQLBuilder.Core/Repositories/SqlRepository.cs
+++ b/SQLBuilder.Core/Repositories/SqlRepository.cs
@@ -70,6 +70,11 @@ public DbConnection Connection
                     if (_dbConnection.State != ConnectionState.Open)
                         _dbConnection.Open();
                 }
+                //DbConnection被using后连接字符串被置为空
+                else if (_dbConnection.ConnectionString.IsNullOrEmpty())
+                {
+                    _dbConnection.ConnectionString = ConnectionString;
+                }
                 return _dbConnection;
             }
             set
diff --git a/SQLBuilder.Core/Repositories/SqliteRepository.cs b/SQLBuilder.Core/Repositories/SqliteRepository.cs
index 275cee8..cf731e4 100644
--- a/SQLBuilder.Core/Repositories/SqliteRepository.cs
+++ b/SQLBuilder.Core/Repositories/SqliteRepository.cs
@@ -70,6 +70,11 @@ public DbConnection Connection
                     if (_dbConnection.State != ConnectionState.Open)
                         _dbConnection.Open();
                 }
+                //DbConnection被using后连接字符串被置为空
+                else if (_dbConnection.ConnectionString.IsNullOrEmpty())
+                {
+                    _dbConnection.ConnectionString = ConnectionString;
+                }
                 return _dbConnection;
             }
             set