How to update sql database table info with excel file using file uploaded - asp.net

Question

I am trying to update the files in the table that I have created. I am using file uploader to insert my Excel file and upload it to the database. But currently my code creates a new database table each time a file is uploaded, which I don't want it to do. I want to just update/replace the whole file in database table. How do I do this?
This is my code:
private string GetConnectionString()
{
return System.Configuration.ConfigurationManager.ConnectionStrings["nConnectionString2"].ConnectionString;
}
private void CreateDatabaseTable(DataTable dt, string tableName)
{
string sqlQuery = string.Empty;
string sqlDBType = string.Empty;
string dataType = string.Empty;
int maxLength = 0;
StringBuilder sb = new StringBuilder();
sb.AppendFormat(string.Format("CREATE TABLE {0} (", tableName));
for (int i = 0; i < dt.Columns.Count; i++)
{
dataType = dt.Columns[i].DataType.ToString();
if (dataType == "System.Int32")
{
sqlDBType = "INT";
}
else if (dataType == "System.String")
{
sqlDBType = "NVARCHAR";
maxLength = dt.Columns[i].MaxLength;
}
if (maxLength > 0)
{
sb.AppendFormat(string.Format(" {0} {1} ({2}), ", dt.Columns[i].ColumnName, sqlDBType, maxLength));
}
else
{
sb.AppendFormat(string.Format(" {0} {1}, ", dt.Columns[i].ColumnName, sqlDBType));
}
}
sqlQuery = sb.ToString();
sqlQuery = sqlQuery.Trim().TrimEnd(',');
sqlQuery = sqlQuery + " )";
using (SqlConnection sqlConn = new SqlConnection(GetConnectionString()))
{
sqlConn.Open();
SqlCommand sqlCmd = new SqlCommand(sqlQuery, sqlConn);
sqlCmd.ExecuteNonQuery();
sqlConn.Close();
}
}
private void LoadDataToDatabase(string tableName, string fileFullPath, string delimeter)
{
string sqlQuery = string.Empty;
StringBuilder sb = new StringBuilder();
sb.AppendFormat(string.Format("BULK INSERT {0} ", tableName));
sb.AppendFormat(string.Format(" FROM '{0}'", fileFullPath));
sb.AppendFormat(string.Format(" WITH ( FIELDTERMINATOR = '{0}' , ROWTERMINATOR = '\n' )", delimeter));
sqlQuery = sb.ToString();
using (SqlConnection sqlConn = new SqlConnection(GetConnectionString()))
{
sqlConn.Open();
SqlCommand sqlCmd = new SqlCommand(sqlQuery, sqlConn);
sqlCmd.ExecuteNonQuery();
sqlConn.Close();
}
}
protected void btnImport_Click(object sender, EventArgs e)
{
if (FileUpload1.HasFile)
{
FileInfo fileInfo = new FileInfo(FileUpload1.PostedFile.FileName);
if (fileInfo.Name.Contains(".csv"))
{
string fileName = fileInfo.Name.Replace(".csv", "").ToString();
string csvFilePath = Server.MapPath("UploadExcelFile") + "\\" + fileInfo.Name;
//Save the CSV file in the Server inside 'MyCSVFolder'
FileUpload1.SaveAs(csvFilePath);
//Fetch the location of CSV file
string filePath = Server.MapPath("UploadExcelFile") + "\\";
string strSql = "SELECT * FROM [" + fileInfo.Name + "]";
string strCSVConnString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + filePath + ";" + "Extended Properties='text;HDR=YES;'";
// load the data from CSV to DataTable
OleDbDataAdapter adapter = new OleDbDataAdapter(strSql, strCSVConnString);
DataTable dtCSV = new DataTable();
DataTable dtSchema = new DataTable();
adapter.FillSchema(dtCSV, SchemaType.Mapped);
adapter.Fill(dtCSV);
if (dtCSV.Rows.Count > 0)
{
CreateDatabaseTable(dtCSV, fileName);
Label1.Text = string.Format("The table ({0}) has been successfully created to the database.", fileName);
string fileFullPath = filePath + fileInfo.Name;
LoadDataToDatabase(fileName, fileFullPath, ",");
Label1.Text = string.Format("({0}) records has been loaded to the table {1}.", dtCSV.Rows.Count, fileName);
}
else
{
Label1.Text = "File is empty.";
}
}
else
{
Label1.Text = "Unable to recognize file.";
}
}
}

Answer 1

The code that creates the tables should give an error when you run it if the tables already exists as you never drop them.
That said, one solution might be to add a check to see if the table already exists in the code that creates a new table; it should be something like:
IF OBJECT_ID('TABLE', 'U') IS NULLwhere TABLEit the name of the table that you want to add, so the code might look like:
sb.AppendFormat(string.Format("IF OBJECT_ID({0}, 'U') IS NULL CREATE TABLE {0} (", tableName));
Another, possibly better, option would be to run a query to check if the table exists before you run the CreateDatabaseTable(dtCSV, fileName);statement. You can do the check by executing something like IF OBJECT_ID('tableName', 'U') IS NULL SELECT 1 ELSE SELECT 0 (this would return 1 if the table doesn't exist), and then conditionally execute the CreateDatabaseTablestatement.