C#读取大文件(四)

心已赠人 2022-04-03 11:57 361阅读 0赞

![InBlock.gif][] \}  
![InBlock.gif][] prgLoader.Value = 100;  
![InBlock.gif][] lblShowPercent.Text = prgLoader.Value.ToString() + "%";  
![InBlock.gif][] btnOk.Text = "关闭";  
![InBlock.gif][] \}  
![InBlock.gif][] \}  
![InBlock.gif][] else  
![InBlock.gif][] \{  
![InBlock.gif][] if(intCount == 0)  
![InBlock.gif][] \{  
![InBlock.gif][] strSelect = strTargetSelect;  
![InBlock.gif][] sqlcmd.CommandText = strSelect;  
![InBlock.gif][] bytContent = new byte\[intLength\];  
![InBlock.gif][] bytContent = sqlcmd.ExecuteScalar() as byte\[\];  
![InBlock.gif][] fs.Write(bytContent,0,intLength);  
![InBlock.gif][] \}  
![InBlock.gif][] else  
![InBlock.gif][] \{  
![InBlock.gif][] int i = 0;  
![InBlock.gif][] bytContent = new byte\[intBlock\];  
![InBlock.gif][] while(i < intCount)  
![InBlock.gif][] \{  
![InBlock.gif][] strSelect = "declare @content varbinary(16) "; //再sql中声明获取目标image列内容的句柄变量   
![InBlock.gif][] strSelect += strTargetHandle; //获取句柄   
![InBlock.gif][] //锁定并读取指定长度的数据   
![InBlock.gif][] strSelect += " readtext " \+ strTableName + "." \+ strColumnName + " @content @start @count HOLDLOCK";  
![InBlock.gif][] if(i == 0)  
![InBlock.gif][] \{  
![InBlock.gif][] //添加@start和@count变量，分别表偏移变量和取的长度   
![InBlock.gif][] sqlcmd.Parameters.Add( "@start",System.Data.SqlDbType.Int).Value = 0;  
![InBlock.gif][] sqlcmd.Parameters.Add( "@count",System.Data.SqlDbType.Int).Value = intBlock;  
![InBlock.gif][] \}  
![InBlock.gif][] else  
![InBlock.gif][] \{  
![InBlock.gif][] sqlcmd.Parameters\[ "@start"\].Value = i \* intBlock;  
![InBlock.gif][] sqlcmd.Parameters\[ "@count"\].Value = intBlock;  
![InBlock.gif][] \}  
![InBlock.gif][] sqlcmd.CommandText = strSelect;  
![InBlock.gif][] bytContent = sqlcmd.ExecuteScalar() as byte\[\];  
![InBlock.gif][] fs.Write(bytContent,0,intBlock);  
![InBlock.gif][] \++i;  
![InBlock.gif][]  
![InBlock.gif][] \}  
![InBlock.gif][] //将剩余的字节写入流   
![InBlock.gif][] int intResidual = intLength % intBlock;  
![InBlock.gif][] if(intResidual > 0)  
![InBlock.gif][] \{  
![InBlock.gif][] strSelect = "declare @content varbinary(16) "; //再sql中声明获取目标image列内容的句柄变量   
![InBlock.gif][] strSelect += strTargetHandle; //获取句柄   
![InBlock.gif][] //锁定并读取指定长度的数据   
![InBlock.gif][] strSelect += " readtext " \+ strTableName + "." \+ strColumnName + " @content @start @count HOLDLOCK";  
![InBlock.gif][] bytContent = new byte\[intResidual\];  
![InBlock.gif][] sqlcmd.Parameters\[ "@start"\].Value = intCount \* intBlock;  
![InBlock.gif][] sqlcmd.Parameters\[ "@count"\].Value = intResidual;  
![InBlock.gif][] sqlcmd.CommandText = strSelect;  
![InBlock.gif][] bytContent = sqlcmd.ExecuteScalar() as byte\[\];  
![InBlock.gif][] fs.Write(bytContent,0,intResidual);  
![InBlock.gif][]  
![InBlock.gif][] \}  
![InBlock.gif][] \}  
![InBlock.gif][]  
![InBlock.gif][] \}  
![InBlock.gif][] bytContent = null;  
![InBlock.gif][] fs.Close();  
![InBlock.gif][] \}  
![InBlock.gif][] catch  
![InBlock.gif][] \{  
![InBlock.gif][] state = 0;  
![InBlock.gif][] System.IO.File.Delete(strPath);  
![InBlock.gif][] bytContent = null;  
![InBlock.gif][] fs.Close();  
![InBlock.gif][] return false;  
![InBlock.gif][] \}  
![InBlock.gif][] state = 0;  
![InBlock.gif][] return true;  
![InBlock.gif][] \}

[InBlock.gif]: /images/20220403/a8d2e0d4634a4642b6f980f7d99fa05c.png