遇到的异常处理

• A first chance exception of type 'System.Data.Entity.Core.EntityException' occurred in EntityFramework.dll

Additional information: The underlying provider failed on Open.

InnerException: {"A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: SQL Network Interfaces, error: 26 - Error Locating Server/Instance Specified)"}

StackTrace: at System.Data.Entity.Core.EntityClient.EntityConnection.Open()

没有连VPN，数据库连接失败

• The name '*** ' does not exist in the current context

刚开始直接在if中定义var keywordfrom1=Convert.ToDateTime(keywordfrom);var keywordto1=Convert.ToDateTime(keywordto);

不应该在if里面定义keywordfrom1和keywordto1变量，导致query中keywordfrom1和keywordto1报错

            var keywordfrom1 = new DateTime();
            var keywordto1 = new DateTime();
            if (!String.IsNullOrWhiteSpace(keywordfrom))
            {
                keywordfrom1 = Convert.ToDateTime(keywordfrom);
            }
            else
            {
                keywordfrom1 = Convert.ToDateTime("1753-1-1 00:00:00");
            }

            if (!String.IsNullOrWhiteSpace(keywordto))
            {
                keywordto1 = Convert.ToDateTime(keywordto);
            }
            else
            {
                keywordto1 = Convert.ToDateTime("9999-12-31 00:00:00");
            }

            var query = db.U_SP_AuditLog.AsQueryable();
            query = query.Where(a => a.ChangedOn >= keywordfrom1 && a.ChangedOn <= keywordto1);    

• A first chance exception of type 'System.Data.Entity.Validation.DbEntityValidationException' occurred in EntityFramework.dll

Additional information: Validation failed for one or more entities. See 'EntityValidationErrors' property for more details.

但EntityValidationErrors不能提供具体的错误信息

将((System.Data.Entity.Validation.DbEntityValidationException)$exception).EntityValidationErrors添加到Watch窗口中就行。

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• CompanyName.Demo.Point.x': cannot have instance field initializers in structs

struct Point
        {
            public int x = 0;//对于结构，不能给里面的变量赋初值
        }

• Unable to copy file “obj\Debug\project.dll” to “bin\project.dll”. Access to the path 'bin\project.dll' is denied

Go to “bin" folder. View the properties of the dll file and see whether it is marked as "Read Only". If read only check box checked, uncheck it.、