如何在 C# 中比较两个 DataSet 列的值？

Question

In below code i want to compare two dataset column's values but its not match then also getting true this condition.so how to really compare?

if (dsEmp.Tables[0].Columns["EmpName"].ToString() == dsAllTables.Tables[2].Columns["EmpName"].ToString())
{

}

Answer 1

You are comparing two column-names, so "EmpName" with "EmpName" which is always true. Tables[0].Columns["EmpName"] returns a DataColumn with that name and ToString returns the name of the column which is "EmpName" . So that's pointless.

If you instead want to know if two tables contain the same EmpName value in one of their rows you can use LINQ:

var empRowsEmpName = dsEmp.Tables[0].AsEnumerable().Select(r => r.Field<string>("EmpName"));
var allRowsEmpName = dsAllTables.Tables[2].AsEnumerable().Select(r => r.Field<string>("EmpName"));
IEnumerable<string> allIntersectingEmpNames = empRowsEmpName.Intersect(allRowsEmpName);
if (allIntersectingEmpNames.Any())
{

}

Now you even know which EmpName values are contained in both tables. You could use a foreach -loop:

foreach(string empName in allIntersectingEmpNames)
    Console.WriteLine(empName);

If you want to find out if a specific value is contained in both:

bool containsName = allIntersectingEmpNames.Contains("SampleName");

If you just want to get the first matching:

string firstIntersectingEmpName = allIntersectingEmpNames.FirstOrDefault(); 
if(firstIntersectingEmpName != null){ 
    //  yes, there was at least one EmpName that was in both tables
}

Answer 2

If you have a single row, this should work:

if (dsEmp.Tables[0].Row[0]["EmpName"].ToString() == dsAllTables.Tables[2].rows[0]["EmpName"].ToString())
{

}

For multiple rows you have to iterate through table:

for (int i = 0; i <= dsEmp.Tables[0].Rows.Count; i++)
{
    for (int j = 0; j <= dsAllTables.Tables[0].Rows.Count; j++)
    {
        if (dsEmp.Tables[0].Rows[i]["EmpName"].ToString() == dsAllTables.Tables[2].Rows[j]["EmpName"].ToString())
        {

        }
    }
}

Answer 3

I have two datatables - dtbl and mtbl, and I use this to return records that have a difference, as another DataTable.

    //compare the two datatables and output any differences into a new datatable, to return
    var differences = dtbl.AsEnumerable().Except(mtbl.AsEnumerable(), DataRowComparer.Default);
    return differences.Any() ? differences.CopyToDataTable() : new DataTable();