- 增加 连接字符串错误时的友好提示；

Providers/FreeSql.Provider.SqlServer/FreeSql.Provider.SqlServer.csproj

@@ -2,7 +2,7 @@
 
 	<PropertyGroup>
 		<TargetFrameworks>netstandard2.0;net451</TargetFrameworks>
-		<Version>0.7.11</Version>
+		<Version>0.7.12</Version>
 		<GeneratePackageOnBuild>true</GeneratePackageOnBuild>
 		<Authors>YeXiangQin</Authors>
 		<Description>FreeSql 数据库实现，基于 SqlServer 2005+，并根据版本适配分页方法：row_number 或 offset fetch next</Description>

Providers/FreeSql.Provider.SqlServer/SqlServerAdo/SqlServerConnectionPool.cs

@@ -121,6 +121,13 @@ namespace FreeSql.SqlServer
             if (_pool.IsAvailable)
             {
 
+                if (obj.Value == null)
+                {
+                    if (_pool.SetUnavailable(new Exception("连接字符串错误")) == true)
+                        throw new Exception($"【{this.Name}】连接字符串错误，请检查。");
+                    return;
+                }
+
                 if (obj.Value.State != ConnectionState.Open || DateTime.Now.Subtract(obj.LastReturnTime).TotalSeconds > 60 && obj.Value.Ping() == false)
                 {
 
@@ -143,6 +150,13 @@ namespace FreeSql.SqlServer
             if (_pool.IsAvailable)
             {
 
+                if (obj.Value == null)
+                {
+                    if (_pool.SetUnavailable(new Exception("连接字符串错误")) == true)
+                        throw new Exception($"【{this.Name}】连接字符串错误，请检查。");
+                    return;
+                }
+
                 if (obj.Value.State != ConnectionState.Open || DateTime.Now.Subtract(obj.LastReturnTime).TotalSeconds > 60 && (await obj.Value.PingAsync()) == false)
                 {